There is cause for some hope.
All during TBC, Shadow priests were the doormats of the damage dealing world. At high PvE content levels they were desired only as a support class because their dps was poor. In PvP they were absolutely hopeless: they had no melee escape, they had no effective CC, they were in cloth armor, and their burst dps was poor. To say that Shadow priests during TBC were pathetic is to accurately state their situation (more for PvP than for PvE where everyone wanted mana batteries).
But ... the developers listened to the community and in WotLK they actually ended up giving to Shadow priests almost all the things they were asking for. They got melee escapes. They were given better mitigation tools, and they were blessed (if you could call it that) with bone chilling amounts of dps.
I think it is more than fair to say that Shadow priests in 3.3 were doing really, really well.
Holy priests are in a situation similar to that of Shadow priests. In WotLK we scaled poorly and became a less desirable PvE healing spec at high content levels. In PvP, Holy priests could be very effective raid healers (which gave them something to do in group PvP), but survivability was so poor that there was no place for them in Arena.
Discipline priests were better in PvP during WotLK, but for PvE at the end were valuable mainly as raid shield spammers.
I'm sure that the devs are aware of the issues that players of the priest class raise. It remains to be seen whether they have the interest and will to take steps to position healing priest as an attractive, competitive class in Cataclysm.
So what you're saying is that if we just wait until the expansion AFTER Cataclysm, everything will be okay again?