As far as a phone/device for mobile games.. Sony is above that shit.. Mobile games generally suck ass.
Another Sony Portable gaming device.. Leave it to Nintendo.
I would much prefer Sony concentrate on their flagship console then try spread the love!. As someone who does not need or care for a portable gaming device, my opinion is biased.
The only thing similar that they should be working on is being able to use any newer Android device to stream games from your PS5.