There are a bunch of older models that have all your qualifications (Toshiba, Fujitsu, Gateway). Search ‘tablet PCs’ and you’ll find most of them. I think the best spec’d model of that generation of tablet PCs was the Toshiba M7 with the NVIDIA GPU, the screen is 14.4".
As far as what’s coming, I do a search almost daily! I’m waiting for the same thing you’ve described - the closest we’ve seen so far is the Asus EP121, but its specs are wimpy. I think they’re introducing an updated model for Win 8. Samsung, Toshiba, Dell and others are back on the tablet march…but most are not spec’d for us, have small screens and aren’t built to run heavy duty.
I’m watching these posts like you are…waiting, waiting.