My money is on ReCore, Super Lucky's Tale, and Ori and the Blind Forest. Lucky and Ori should be able to run on Switch easily since neither is that graphically demanding. ReCore would need some downgrading, but nowhere near as much as any of their AAA games would need. Rare Replay might be a possibility, but would be too much work I'm sure, porting 30 games to Switch. Some individual Rare ports might happen though.
I would imagine that some last gen games would also be on the table. Perhaps master chief collection or Gear of War 1,2,3 would be possibilities. This would certainly help to create more fans of these respective franchises.