You can always tell in these threads who grew up in the ps3/360 generation. Five years is pretty much the norm for a consoles life cycle, before falling to second string in favor of its replacement.
With good gpu, ram, and CPU's out there, as well as dirt cheap 4K tv, Sony and ms would be silly to rest in their laurels. The xb1x can hang for a bit, but games will be held back in ways until a new console can arrive.
I think we'll see Sony make the pro the base console, and the ps5 the new top end. Late 2019 is my guess for release
Can you? I didn't grow up in the PS3/360 generation (was an SNES/Genesis kid) yet five years still seems rather short for this life cycle given the nature of the mid-generation upgrades. Plus, it feels like people are more interested in 2020-2021, which is closer to 7-8 years.