TL;DR - Summary at bottom.
As I am writing this the 4.0 patch hasn't been implemented onto the EU servers yet (it will be tonight). It has been over at the US servers however so us on the other side of the pool of water are getting some small reports on what things seem to be like. Most people are actually too busy figuring out back from front to report anything useful it seems. We all need a week or so to let this sink in, run some raids and gank some alliance (or horde, if you play it that way, ahem) before we can say A or B or "THIS IS SHITE!". Hopefully you've been keeping yourself up to date with all the changes and have some general idea on how to reforge your gear, respec, regem and reglyph. There are plenty of blogs out there with more or less comprehensive guides on how to do this. I myself have written guides on what I think you should talent as a disc or holy priest.
But speaking of glyphs, it might actually be worth mentioning what we should get ourselves. First of all, we're getting a new set of glyphs, the Prime Glyphs. They've also changed how glyphs work, so that you learn them now instead of sort of "gemming" them onto your char as they've worked before. Once you've learned a glyph you know it, and won't have to buy it again. Instead you can pick and choose from a list whenever you need to replace glyphs. You do need reagents to remove a glyph however, something called Vanishing Powder or similar.
I've been giving the glyphs a looksie and I can say, our picks are actually rather simple. The obvious choices are just many enough to fill the slots we've got. Only in a few cases does it boil down somewhat to how you want to play, so I'll take you through them and give you suggestions. In some cases you can choose what works best for your playstyle.
There are actually only 3 prime glyphs worth taking for the disc priest, so the choice is really simple.
Penance - Oldie but goldie. One of disc priests best and most important spells. Even if it probably will be used less now that alot of other heals have entered our arsenal, the potential of Penance has always been great and increasing it further is a smart thing to do. Penance delivers when you need it.
Power Word: Shield - The disc priest signum, the shield. This has long been one of the best glyphs for disc priests, and even if I think we might move away from shield spamming somewhat come Cataclysm (at least I really hope so), this will still be a really important part of our healing style.
Power Word: Barrier - A completely new spell that I've had no chance of testing at all yet. The alternatives to this glyph however aren't especially good, so it still seems like we'd get the most from glyphing this.
Divine Accuracy - Will provide us with all the hit we need to actually be able to do some damage with our smite (even though that actually is a secondary component of us using it). This means we won't have to stress dpsers out by needing on hit gear, or even worse, reforge some hit onto our healing gear.
Smite - This glyph will increase the damage of Smite if the target is afflicted by Holy Fire. I am ambivalent about this glyph. I don't think we should see it as forcing us to use Holy Fire in our rotation. I think we should see it as giving us an extra bonus every time we have the time to put Holy Fire into our rotation. Although Blizzard wants us to be pew pew priests, there is still alot of healing to be done that Atonement won't cover. Using a gcd for Holy Fire every 7 seconds might not be something we've got time to do. Remember that increased damage on Smite equals increased healing with Atonement, so this is still a very good glyph. EDIT 16/10: I wrote this after testing it some - "I have some questionmarks regarding Holy Fire though. The dot isn't up as long as the cooldown of the spell, which means there is a gap where the dot isn't applied and the spell still isn't available. Also, we don't have any hit affecting this spell which means we might (and probably) miss with this spell alot. It makes me wonder if Glyph of Smite is worth taking. But as I argued in my post about glyphing, it's more of a bonus than anything else, and there really isn't much of an alternative either."
Dispel Magic OR Mass Dispel - Simply because there is nothing else to have. 3% healed when dispelling isn't awesomely much, but neither do we cast Mass Dispel that often. I think both of these glyphs are about equally good in a pve setting.
Same old boring unfortunately!
Shadow Protection - If you already have a priest designated to be the Shadow Protection user with this glyph, you might not want it, otherwise it's a decent minor glyph since it increases the duration of Shadow Protection by 50%.
Shadowfiend - In lack of better glyphs, this is a good one (generally better for pvp though).
Fortitude OR Levitate - Fortitude is great in that it saves you mana for when you're rebuffing people mid combat. Levitate is great in that you don't have to run around with a bunch of Light Feathers all the time (and die when you thought you had one but didn't). If you never move outside the raid you might not need levitate as much though.
Shackle Undead? -
As with disc our choices are fairly obvious. But there are some questionmarks worth mentioning.
Renew - Renew will still be our most important heal, so this one is a no-brainer.
Guardian Spirit OR Prayer of Healing - I'd say Guardian Spirit is better for instance healing and Prayer of Healing is better for raid healing overall. If I had to choose one I'd go with Prayer of Healing as it is now. I use that far more often than GS.
Lightwell - Now in Cata the content actually requires people to use a skill like Lightwell, and to my experience they're generally quite good at doing this. This is a really strong glyph, increasing the total effectiviness of the Lightwell by 50%, and I strongly recommend it.
Flash Heal? - I don't use Flash Heal that much when holy healing today. Increasing the crit chance of the spell by 10% on targets below 25% sounds a little weak in my ears, although it does synch with Inspiration.
Very few strong Major glyphs forces us to take a couple of weaker glyphs instead.
Circle of Healing - For the raid healing priest this has always been a great glyph, and will surely stay that way in 4.0/Cata.
Dispel Magic - See above.
Mass Dispel - See above
Spirit of Redemption? - IF you are taking this talent, this is probably a good glyph to go along with it (just replace either of the dispel glyphs). You really shouldn't take this talent however.
Psychic Scream? - If you feel like you need to help out with the cc in heroics, this could be a good glyph to keep handy.
Holy Nova? - I've long been wondering if Holy Nova might not be used as a really nice aoe-heal. Problem with it is of course its very limited range. If you find yourself in many situatuions where people are huddled together, the effectiviness of Holy Nova could actually become better than PoH (especially in a 25man raid).
See above for disc priests. Holy will use the same ones.
So to conclude, for 4.0 I'd use;
Prime: Penance, Power Word: Shield, Power Word: Barrier
Major: Smite, Divine Accuracy, Dispel Magic
Minor: Fortitude, Shadowfiend, Shadow Protection
Prime: Guardian Spirit OR Prayer of Healing, Renew, Lightwell
Major: Circle of Healing, Dispel Magic, Mass Dispel
Minor: Fortitude, Shadowfiend, Shadow Protection