I've attempted some trash in the 10 man version of BoT with my Pally+4 DK's. I wiped about 10 times, but that was mostly due to A) Not having one of them geared as a tank, and B) having zero reliable CC. If I had had another 5 boxer or 5 individuals it'd have been totally doable.

My gut feeling is that it's mostly a gear issue. Cata heroics are as hard as TBC heroics were at launch. There's no free epics like there were with the Wrath launch to help you get through heroics. My guess is that once you've got the appropriate gear 10 mans will be doable solo--Perhaps not all of them but some of them at least.