Loremaster is the one that intrigues me most. So much of Azeroth is being so profoundly changed in Cataclysm that it's difficult to imagine this achievement staying exactly the way it is. If nothing else, I would imagine that Blizzard plans to change the number of quests required on each classic continent to get it, but there's another thing -- will the new 80-85 quests in places like Deepholme and Hyjal count as "Eastern Kingdoms" and "Kalimdor" quests, or not? Do they get another zone classification entirely? What about things like the newly renovated Azshara?
If the current quest totals stay the same and if the new zones count towards them, that changes Loremaster from an achievement you've really got to go out of your way to do into something that you can get without much fuss on your way to 85. If Loremaster doesn't become a Feat of Strength (which is also a possibility, I guess), I wouldn't be surprised to see the requirements increased.
Glory of the (insert tier) Raider
Similar to the fashion in which the Amani War Bear disappeared from the game with patch 3.0.2 (when the talent, skill and raid buff changes would have made getting it hilariously easy), Blizzard removed the black and plagued protodrake rewards from tier 7's Glory of the Raider. Later, they said they weren't that happy about it; lots of players were apparently screwed out of a drake solely by the RNG nightmare of Immortal, and many of the achievements were difficult regardless of gear.
But even things like the Ulduar-10 rusted protodrake are relatively easy to get these days, and experienced guilds have been selling them for close to a year now. Between the ICC zone buff going to 30% and player scaling at 85, should we expect Blizzard to axe all of the Wrath raiding rewards?
Personally, I'm for keeping the drakes and titles in the game -- I think they're a really neat thing to do at any level -- but there's no denying that all of Wrath's raiding achievements are going to be a lot easier at 85.
A Tribute to Immortality
This one's pretty much the same deal as its Glory of the Raider cousins, but (I suspect) much more affected by an entirely different game change. Blizzard's been pretty vocal about the increase to player health totals going live with either the Cataclysm content patch or the expansion itself, in part because it wants to tune boss encounters around less "spammy" healing. The general idea is that healers won't be blowing every single GCD in an effort to keep tanks from getting two-shot and 3-4K/tick AoE from wrecking your raid. With higher player health, healing efficiency will also decrease.
Anyone who's tried for a perfect 50-attempts run through Trial of the Grand Crusader can tell you that losing people is almost a given. Even Ensidia, commenting on their world first (three months after patch 3.2 was released), admitted that you have to be pretty lucky, and never more so than on Faction Champs. If you can get through this fight without having a cloth class targeted, zerged and annihilated at some point, well, you're a better man than I am, Gunga Din. I've seen a player die in a third of a second that way, and while my healing reflexes are pretty good, they're not that good.
With significantly increased player health totals, the odds of a player being burst down during this encounter nosedives, so I'm curious to see what happens to this achievement.
Well, the world's being blown up. It stands to reason that whatever you saw previously probably doesn't exist anymore.
On the now-vanished list of achievements previewed by MMO Champion, I recall seeing one that required you to "survey the damage" (or something to that effect) done to each portion of the world, rewarding an entirely separate achievement from World Explorer. I doubt it's possible to do both at the same time unless you receive a simultaneous achievement for time travel.
I'm guessing that the sub-achievement for exploring Outland (and possibly Northrend) will stay the same, but I'd be shocked if you weren't required to re-explore the newly-augmented Eastern Kingdoms and Kalimdor for the Explorer title. Either that, or World Explorer becomes a Feat of Strength, and something like "the Surveyor" replaces it for all new-fledged Cataclysm explorers.