In March, Valve ran the Steam Game Festival: Spring Edition, a showcase of more than 40 game demos that had been destined for GDC before it was cancelled by the coronavirus outbreak. It's coming back this June.
The Steam Game Festival: Summer Edition will run June 9-14, and will once again offer demos or "short playable experiences" for games scheduled to come out within the next year. The spring event was indie focused, and that'll probably stay true, though this one could be a bigger tent given that it gets underway on the same day that E3 2020 was meant to.
No details beyond the dates have been provided, but this is the first "big" online event to be nailed down since E3 was cancelled—and, more specifically, since the ESA scrapped its plan to hold an "online experience" in place of the 2020 show. Microsoft has committed to an online presentation in lieu of E3 this year, Ubisoft and Electronic Arts have said they're looking into it, and Devolver Digital still plans to go ahead with its Devolver Direct show, but none of them have confirmed dates as of yet. Our own E3 event, the PC Gaming Show, will also be happening this June.
If you're a developer and you'd like to take part in the show, you've got until April 24 to sign up. Full details, including requirements for demos, an "artist statement," and optional live presentations, are available here.