Why switch and not ps4? Their games would be much easier to port over to and gamepass would be much more profitable on the ps4.
Nintendo and MS have had a very good relationship the past year or two, with Nintendo choosing to implement crossplay with Microsoft many months before Sony finally warmed up to the idea of crossplay. Makes sense to me.
If Google does indeed release a next-gen console like some rumors suggest, Microsoft's and Nintendo's best hope of surviving the dual onslaught of Sony and Google would be to partner with each other, in theory at least.