I look at what Nintendo has done with the Switch, and it seems to be working out very well for them. It turns out, a console that doubles as a handheld is a more attractive option for people over a handheld with console-like power. Should Sony follow suit with a future iteration of the PS4? Sure, they could buy a Vita for remote play for the current version, but would it be better to have a device that's a PS4 at heart? Not to compete with Nintendo or anything, but for the convenience of people that prefer gaming in such a manner.
Granted, such a repurposing would come with sacrifices. Likely a smaller hdd option and physical games would change formats, splitting the base, And it would surely come with its own version of a dock if they can't shrink the innards to a proper tablet size. Would it be a good idea in the end?
