Cancelled possibly due to the lack of interests from fans. Something Blizzard stuffed up on.
For most fans I know, this is the only reason they wanted OW2. I stopped playing because the 'update' they did wasn't really to my interest, making it free and rmoving cosmetics as rewards, taking away any kind of progression in a game I'd paid for but had hopes the PvE adventure mode could live up to their hyped standards.
I expect the interest in the game to die quicker now.