Zarhym expressed a lot of feedback about the upcoming major content patch 3.1 and the 25-man / 10-man dungeon Ulduar.  Content patches will be released at a fair pace, but not as often as it happened in Burning Crusade to allow guilds breath-space with raid progression before moving on to a new dungeon.

Blizzard Quote:
Our development team is currently hard at work on Ulduar. It’s going to be massive. For those looking to progress past Naxxramas, this will be your place. For those looking for much more of a challenge content-wise than they’ve seen thus far in Wrath of the Lich King, Ulduar welcomes you.

After The Burning Crusade’s final major content patch, the plan was to space out the new raid dungeons in Wrath of the Lich King so there wouldn’t be overwhelming moments or times where several raids are released at once and slightly ill-tuned (as was the case with The Burning Crusade’s launch); we also don’t want extremely long periods of time where no new raids come out, as was the case after The Burning Crusade’s initial launch.

I trust players can expect to find a fair amount of challenge and content with patch 3.1, and each major content patch after that in Wrath of the Lich King will offer similar new feats.

Raid progression in this game has always been fairly linear. That is by design. The idea is to have clear progressions depending on how you choose to spend your time, whether in 5-man, 10-man, 25-man, or PvP.

It takes quite a bit of time to design a new dungeon, even just speaking about the art alone. By the time we get around to tuning a new raid dungeon, the idea is to offer new, more difficult challenges, which would naturally result in better rewards. That seems to describe a linear design philosophy as you put it.

For those asking about the challenge, I’d wager the average guild couldn’t expect to waltz into Ulduar and clear the place right away in its top form. If it didn’t come back to haunt me (har), I’d guess it would take weeks for the average guild.

You might see some additional rewards from heroism vendors down the line, though it’s not expected there will be a host of new items released comparable to Ulduar or Icecrown loot, at least not in the same manner Sunwell badge gear was provided.

As we continue to evaluate professions, one shouldn’t rule out additional glyphs in the future. The achievements will continue to come, and there will always be plenty of achievements for everyone.