I'm of the opinion they should do a Banjo-Redooie, an N-Sane Trilogy style remaster of the two games so that whoever does the remaster has already worked out the kinks of how to make a Banjo-Kazooie game before moving on to a Threeie. I feel like going straight to a Threeie risks running into doing too much at once, having to recapture the essence of the old ones while making something new. Do the former first, before doing the latter.
As for my realistic expectations, I was hoping Xcloud on Switch so in addition to playing the Banjo-Kazooie games, I could also play high end titles that couldn't natively run on Switch, but insiders have said Nintendo is against most streaming services coming to the system. Nintendo just knows how to perpetually miss opportunities. Outside of that, either ports for NSO N64, or Rare Replay on Switch. Though, if they do Rare Replay for Switch, please change the box art so the N64 versions are on the cover!