Blizzard Entertainment President J. Allen Beck released a statement regarding the situation and it did very little to appease anyone. This is according to the official Nintendo NY Twitter account, which didn't really have any more information to share on the matter, beyond making it clear that the cancellation was very much Blizzard's call. It's been announced, however, that the event has been cancelled.
After Blizzard suspended Hearthstone Pro Blitzchung for using pro-Hong Kong rebellion phrases during a livestream, the #BlizzardBoycott has been going strong. Nintendo announced the event's cancellation late on October 14... With calls to protest BlizzCon mounting at an ever growing pace, it's highly likely that Blizzard anticipated the same would occur at Nintendo's New York City store during the special Overwatch Nintendo Switch launch party, and cancelled the event to avoid the bad press.
If you somehow managed to miss last week's turbulent events, Blitzchung appeared during a post-game livestream where he came out in support of the ongoing Hong Kong protests. Further, Blizzard had said its broadcast were exclusively for focusing on games despite previous broadcasts championing social causes. Still, there will always be many gamers who prefer owning physical copies of games, but if you're in that camp and you're planning on picking up Overwatch tomorrow, you might want to skip the physical copy and just buy directly from the Nintendo eShop.
Considering all of the controversy surrounding Blizzard and Activision, one has to wonder about BlizzCon 2019. In my experience with video game events, I'm betting there were to be mini burgers and muffins.