Ultimately I think it may be pointless because PiP systems on TVs are getting better all the time, by the time they have very powerful + inexpensive SoC's in TVs, and the spatial resolution/image processing has reached a sort of limit we'll see them spend the processing power on other things like PiP.
My TV does PiP right now, as do all X1E+ Sony TV's, I think LG and Samsung do on the higher models too (In fact one of them had a much better implementation in either 2019 or this year if I remember), but its usually limited to showing other HDMI inputs, so you can't show youtube or netflix or an app in a PiP while you view an HDMI source, at best you can do it the other way around on the newer Sammy/LG I mentioned in brackets above, ie HDMI source PiP while using an app. On my Sony it only works with HDMI sources, its disabled when viewing apps.
I can see how QMS (Quick Media Switching) might help out in some way, because it would possibly allow showing different refresh rates and resolutions within the same frame, if the OS supported it. I think the current idea behind is "just" to reduce the time it takes to switch between modes, so no more/heavily shortened black screens when going between HDMI inputs or apps.
