Sony will be on the list eventually, they just haven't yet announced their event - It's rumoured for late May - early June.
Here's Phase 1 of the line ups with more to be announced, not all of these will have big digital events but they'll be announcing stuff.
Nintendo is unknown, I don't believe they're taking part in this Game Fest thing and they've mentioned no Direct for June with reports it might not happen until the end of Summer.
Some other bits have been announced but haven't yet got exact dates, Xbox is planning a Game Festival like Steam and also announcements every month, with their June announcements happening in IGN's Summer of Gaming.
Should be more announcements coming soon.
Ah so it's just Nintendo that doesn't want to play ball, typical.
Anywho this is thread is an undertaking, I imagine it can be difficult to keep up with all these companies doing different things at different times over the course of four months, but I'm sure you'll do a fine job.