I think PiP is more something they would look into, allowing all Media apps like YouTube, Netflix, TV+ etc... to do PiP in throughout the OS.
But I am not expecting big features in iOS 14, I think they are going to use it to correct all the gremlins and exploits in iOS 13.
Maybe iOS 15 will bring some more fully fledged multitasking.
Either way, I barely used Splitscreen on my Androids, I actually do not miss it, it’s more a nice to have feature than useful, IMO, I used it a lot on my Note8 for a little while in the beginning then slowly stopped as I got over the novelty.