I see it like a revision of the current hardware with Hdmi 2.0 and 4k scaler (not new GPU)
This case is best case scenario imo, because:
- It wont fracture the userbase and upset PS4 owners, Current owners won't feel the need to upgrade.
- Current PS4 won't struggle to play the (enhanced games) and WILL play all games till the end of the gen.
- PS4.5 would be enough of an upgrade for some enthusiast who wanted slightly better performance and Res upgrade.
- Sony can go all out on PS5 and make 4k " games " dream a reality.
Edit: Sony has been doing this almost every gen to some degree, They added a screen attachment to PS1, Internet ports to some slimmer PS2 versions, PS3 era they removed some features (BC+ ports) in a slimmer package.
This time change seems to be more radical but not by much really .