I own a psp go. I think a chunky (thickness) and larger one would be interesting. My psp acts as a clock when docked which is cool. But I think slide is dead as people have said. The buttons on psp are very thin. Certainly be hard to do trackpads etc.
Major Problems with game industry right now... Cost to make a game, and from that the repercussions if it fails.
Making an engine doesn't happen overnight, and then you need new Devs to learn that engine throughout its lifetime. Fine for a big player, but even a large company like CDPR had issues, hence moving.
It's a shame, but you can't write off engines like UE. Epic and the Coalition do incredible work with it. UE5 is still VERY new. Look at Fortnite and wait for the next Gears game. Even if the game is dull I'm sure it will be a showcase for UE5.