Is now possible with Bay Trail processors. I've been playing on Dell's Venue 8 Pro. Performance is surprising. My frame rate is typically around 40-60 and turn times are quick. Overall, a great experience. My only complaint is that clicking small items can be difficult.

The battery lasts about 4 hours with brightness around 33% (plenty bright). 5+ hours is possible by limiting the max proc state to 50%. Even with the proc limited, my frame rate hovers around 30, which is sufficient for a turn based game like galciv.

Some other bay trail tablets worth checking out:

Lenovo's Miix 2 (also called Miix 8), and

Toshiba's Encore.