I swear this question is asked at least once or twice a year.
I'd be happy with it. I'd also be happy with Sony/Microsoft going multiplatform. But its not going to happen, because Nintendo are doing very well at the moment.
As it stands though, im not really invested at all in Nintendo's suite of exclusives. I have a Switch, but the only Nintendo-exclusive games that I own are Mario + Rabbids Kingdom Battles (because it is basically XCOM), and Mario Kart 8 (because arcade racing).
I don't care for 2D or 3D Mario. I don't care for Zelda. I don't care for 2D Metroid. I don't care for Smash. I don't care for Pokemon. etc
So even if they did go multiplatform, I wouldn't see my purchasing habits change much at all.