This thread is where I'm gonna put information on MMOs that are running some sort of Pride Month events. It will be updated as time goes on and the information rolls in. Honestly expect most of this to start coming in May, though WoW's news was really early.
Official Events
World of Warcraft (retail) - Added March 29
News post: https://www.wowhead.com/news/darkspear-dash-wows-first-official-pride-event-coming-in-patch-12-0-5-380974 (https://www.wowhead.com/news/darkspear-dash-wows-first-official-pride-event-coming-in-patch-12-0-5-380974)
Looks like the annual community Running of the Trolls pride event is officially supported
Community Events
There likely will be a few, and I'll add them when I find out about them.