or maybe a arm structure?
IF they go to ARM they will loose compatibility again, they made great sells mantaining compatibility between PS1 and PS2. If they keep it this time, and considering how the PS4 is selling and the base it can make, then PS5 can be a hell of a seller too. I dont think they will take compatibility out.
its all about costs. we dont know the structure of the market in 5 years, if mobile games are realy growning fast, we could see a switch to arm based gaming.(and it would make a ps5 tab possible, nobody cares if a tab costs 7 or 800$ as long it is cool)