Its official -- Sunwell Plateau is the real deal.

[Ave07]

9?!?! You are fine with 4-5, even 3 but 4 is very nice. But 9!

Yeah it was for week one only.

We now run 4-5 warlocks now..

[Nitros14]

I think it's going to be possible, Ulduar gear isn't really powerful.

You'll walk out of T7 decked in 213 pieces alongside a handful 226 from KT, Sarth +3D and Malygos.
Ulduar 25man drops 226 pieces, meaning that you're not too far behind on the power curve, the only really powerful pieces in Ulduar are the Hardmode 239 Items, but those are pretty rare and everyone will merely use a handful of pieces even in BiS.

Then there's the entire question about pre nerf and post nerf.
Ulduar is a massively nerfed raid, check patch history for every Ulduar Boss on wowpedia, pretty much all of them got nerfed / fix in some fashion.

If Blizzard truly intents to launch the enterity of Wotlk post nerf, Ulduar will be much easier than it was in 2009 when it first launched.

Nevermind that as another poster just said, you know which classes to stack for Ulduar, Yogg+0 in particular.

Yogg-Saron was nerfed an incredibly massive amount when Trial of the Crusader came out, it'd be a pretty pathetic fight on day one if they launched it like that.