Hopefully 4/5 years. Anything longer is too long.
Same with PS4 and Xbone.

Yeah, especially with how underpowered the PS4/Xbox One are in comparison to their predecessors. 5 years seems pretty good.

Well, rumours suggest that it's more of a home console/portable console hybrid type deal, and something about a unified network across multiple things.
Something like that. Look it up.

Will do, thanks.