Nokia will license out their name to Foxconn and other Chinese phone manufacturers from 2016 (with their launcher on top).
I think the current leadership is burnt out on phones, there's no desire to go back there. They have nothing left of their mobile division - which was a money sink anyway - it all went to Microsoft. The only entry I can realistically see would be a Jolla-like, small team, Android or Meego-esque OS. But them they wouldn't be able to license their name so easily, so the opportunity cost wouldn't be worth it.
As for the 808, I'd expect it to run well on pretty much any processor. For one, look at the screen resolution. Android phones may have been fairly laggy at the time, but I think the Galaxy SIII (which released in the same month) would've run Android fine if it needed to display only 230k pixels, instead of the 921k it actually did. Anyway, Nokia's actually doing fairly well now. They've adapted before, this is just another change of face.