We're only a day into 2009, and we've already got an update on one of our predictions. Vaneras has appeared on the EU forums talking about Ulduar's difficulty level and he says that yes, it will make a PTR appearance, and yes, it will be hard, but probably not in the way that we'd expect. He says that Blizzard is pleased with the way the "Sartharion with no drakes" worked, so they're planning to expand on that idea in the upcoming raids, by including more "hard modes" and more achievements, with "an increase of reward level if successful."
So the odds are that we'll still see Ulduar's normal mode downed within days if not minutes on the live realms -- it won't actually be "hard" in the sense that the guilds with high level gear won't be able to plow right through it. But there will likely be multiple challenges within that are very hard, and achievements that will likely reward special gear or titles that will take guilds a while to do. This probably won't satisfy most of the really hardcore raiders, but we've been over this one -- Blizzard would rather have the majority of the playerbase play these raids, and since challenges and achievements don't take as much development time, that's what the minority of really hardcore players will get.
Of course, as with everything, we'll have to see how it works out -- Blizzard is clearly trying to make sure everyone coming to these raids finds what they're looking for in terms of a challenge. Ulduar itself might not be as hard as we predicted, but if Blizzard really ramps up the "hard modes" within the instance, it could be a while before we see anyone able to topple all of the challenges in there.