8700k is previous gen? Link 9700k please, I didn't realise it's out.
Intel has had 4 generations of refinements with this architecture, each time changing the socket (requiring a new motherboard for an upgrade) AND it has severe vulnerabilities to boot.
AMD hasn't lost anything, they've produced a highly competitive product at a highly competitive price and they have further refinements and upgrades in the works which will operate in the same socket.
If I built right now it'd be AMD for sure, they currently perform well enough for a quality experience in all games and an upgrade is an option in the next couple of years too.
If the OP buys an 8700k, short of buying a new motherboard, that's what he's stuck with for the life of the machine.