After a rather interesting (Blizzard) yesterday, it looks like Overwatch hasn't been totally ruled out for the Nintendo Switch.¬†
Granted, it's not been ruled in either, but it's an interesting thought. Overwatch is a success on both console and PC, so a Switch release seems almost natural to follow. The big question is whether it would be practical or not, even with the Switch's portability.
When asked about the possibility, Kaplan responded with, "I'm loving the Switch! My second favorite gaming platform of all time is the 3DS. Getting OW on the Switch is very challenging for us. But we're always open minded about exploring possible platforms."