Yepp, I am quite sure that if there is such a handheld, there will be mandatory support for it.
That way they will be able get a huge game library for this device fast. If the gamer does not know if games come to the handheld, he wont buy it.
Of course Sony has to make sure, that it is powerful enough to port the games easy by reducing resolution and features or whatever.
The Xbox Series S had for example the problem that the memory was much smaller and some parts of it extremely slow compared to the main device, which made some ports extremely difficult to impossible...