Ryan said he expects up to four years for the PlayStation 4′s expected life span, which makes sense considering the console’s large install base. The PlayStation 2 had a life span of about 13 years, and developers continued to support it several years after the PlayStation 3 approached its middle age.
“The PS4 community will continue to be incredibly important to us for three or four years,” Ryan said. “Many will transition to PS5, we hope if we do our job well, but tens of millions will still be engaged with the PS4.”
Basically console generations are kinda over as you knew them. You will have these kinds of "phased transitions" as a standard I think for everyone.
I'm a bit confused by this opinion when every PS console since the PS1 has overlapped with it's successor for a few years. There's always been phased transitions. It's not a new concept.
Anyhow, this makes logical sense. The PS division makes so much money off it's network services that of course the PS4 will continue to be supported past the PS5. What is a little disappointing, though entirely in line with how Sony goes about their 1st party offerings, is that certain games which seemed next-gen only are indeed cross-gen. Perhaps the insiders saying that Sony has moved all PS4 development to PS5 fueled the expectations, but again it makes sense.
Sony doesn't need you on the PS5 day 1. The more embedded you become into PSN on PS4, the less likely you are to move to anything else but the PS5.