I really hate to be a downer, but I think "hope for the best, expect the worst" is important here. The fact that at least three games are being bundled together makes me think that Nintendo is not going to put a lot of work into them. I think it'll be similar to the Kirby collection from a few years ago, with essentially rom dumps of 64, Sunshine, and Galaxy.
I imagine 64 will be more or less a virtual console port. Sunshine might have some work done to the water pressure of FLUDD, but since you never need anything other than full force, I can imagine Nintendo just making right trigger fire FLUDD at full power then maybe right bumper let Mario run around while spraying. Galaxy will likely be the Nvidia port. Galaxy 2 is probably not included because of the Yoshi tongue and Nintendo not wanting to do significant work to make that work on Switch.
If Nintendo are actually making significant changes, I imagine this is the next big 3D Mario project on Switch. I would not imagine an Odyssey 2 coming out soon if Nintendo is running 64 in the Odyssey engine or anything like that.
But then again, I could be completely wrong, and I would love to be.