Valve promises there will be “hundreds of demos” this year, and while it has not shared what it can play for the upcoming event, there have been some notable games unveiled last June, including Sable and Toem. It seems likely that Valve will be promoting games that are great for the Steam Deck and hopefully by that time, many more people will have received their long-awaited bookings. (Unfortunately, the projected availability of orders for the third quarter means that I am very likely to lose, at least when it comes to trying out mobile games.)
Scheduled in mid-June means that Steam Next Fest will be timed exactly when E3 usually happens. While E3 organizers have stated that the trade fair will not be held in person this year due to “the continuing health risks surrounding COVID-19”, they have not announced specific dates for the event.