Apart from the fact we won't have finger-tracking technology as sensitive as a dual-stick input next gen, it's not a matter or input accuracy but actual usability. Shooters want buttons. Hard-core Halo and Gears and MW players aren't going to be happy to point at the screen shouting ratatatat to shoot, or wiggling their thumb up and down. And do really feel pretending to hold a controller is going to work even if the accuracy were there? You think players are going to be happy moving their thumbs in mid-air and squeezing non-existent analogue triggers?
Something to hold and interact with is essential for some experiences. A console that forgoes buttons is marginalising its userbase. If you only offer arm-waving Minority Report interfaces, you lose all the gamers who come home from work and just want to sit back and relax playing their games. As there's no need to forgo buttons as they work perfectly alongside camera interfaces giving the best of both worlds, you want both packed in from the off. If I were to pick one over the other, I'd pick the conventional controller as you can do more with it for comfortable sit-down gamers, although this gen I was hoping and expecting Sony to bundle a camera with the PS3 as it's clearly the best situation for everyone.