Probably the same 10 hour life, smaller battery for a slimmer design ( I doubt though that it will be a different design) and a much more energy efficient processor.
Yep, can't see why it would change much. Any efficiencies will be possibly countered by some other feature that uses more battery. It will be about the same though.
Yeah, I expect something similar to iPad 4 and iPad Air. iPads generally have good battery life, so I don't expect the Air 2 to differ, maybe 12hours of heavy usage?