During an investors call, Ubisoft CEO Yves Guillemot stated that he believes the current generation of consoles still has another two years of life left in them.
"As Sony launched PlayStation 4 Pro last year and Microsoft Xbox One X this year, we think we still have a minimum of two years in front of us before something new is coming."
If the PS5 were to launch in 2019, that would put the PS4's lifespan at 6 years. Which is one year less than the PS3 had. With the release of the PS4 Pro, I'd expect this generation to last longer, instead of getting shorter, and see a new console in 2020. But who am I to argue with the head a Ubisoft!