If you're going to call 650B "27.1" then you should call 26 "26.1" and 29 "28.6". There's only 2.5" between 26 and 29 however you look at it.
I like you, that's my kind of pedantry!
Seriously though... 29er's ain't dead, far from it. In fact 26" ain't dead, whilst there's still a call for it (and there pretty much always will be) then somebody is going to make the frames/forks/rims.
Anyway... Had a quick razz up and down the road on Stanton's pre-production Switchback the other day... BIG thumbs up! It's unapologetically a HT bike for chasing down DH bikes on technical terrain. It's still got a really short chainstay though even with the 650b wheels, and manuals/wheelies better than most 26" bikes.
Also had a quick spin on the pre production Sherpa 29er, and obviously it's a much more XC focussed frame, but the geometry is still spot on for a thrashing and is pretty short for a 29er.
If you really want a hardcore thrashable 29er that handles well though, look at something like the Canfield Yelli Screamy. Chainstays as short as most 26" bikes, and built to take a right thrashing.