Except for the part where Loken makes it very clear that he follows Yogg-Saron.

More likely turn of events?

Yogg-Saron has somehow infested Ulduar and the place is a hive of Old God minions now. Titan creations affected by the Curse of Flesh and driven mad by the whisperings of Yogg-Saron roam the halls, just waiting for tasty adventurers to pop in for a snack.

Yep. It's gotta be Yogg-Saron in Ulduar... or atleast affecting Ulduar.

I have the distinct feeling that the first few bosses in that place will be Tyr, Hodir, Freya and Mimir due to some mind controllyness that forces them to do the Old gods will. Swiftly followed by Thorim quite likely and then maybe Loken(If his demise in HoS was soemwhat exagerated) before possibly Yoggy himself. Makes a bit of sense though I was also under the impression that Yoggs was under Grizzly Hills trying to grow a tree. So possibly we'll see a Yogg related lackey if Loken doesn't fit that role himself.

I only hope we can liberate the watchers rather than slay them in the battles. I've really enjoyed the lore of stormpeaks so far and it'd be a shame to slay all of those guys... i'd rather like to have a quest chain to return them all to their temples again(phased perhaps)

Another interesting thing to consider is the Faceless ones under Icecrown, how closely related is Mr Saron to the Lich King? First name terms? I've got to say future content patches have me most intrigued in Wrath.

We know almost for a fact that Yogg-Saron is in the unnamed raid in 3.2. Therefore, I think

MASSIVE SPOILERS

that a corrupted Thorim will be the final boss. After he was taken to Ulduar, who's to say Loken didn't pass his corruption on before his death? Maybe all the watchers (and, not to nitpick, but I THINK the term might have been Keepers) will be bosses in one form or another.