Think about it, if Capcom can do cross-play and cross-save with MHXX on 3DS and Switch, then you know Gamefreak can with Pokemon. I've read (and partook in) debates back and forth for which console Pokemon Stars would and should be on, but there is no excuse now, and nothing holding Nintendo and GF back from making it happen. Just like with MHXX, everyone wins.
I tried embedding the video, but it's not working for me. You can find it in that link though.