Personally, I would like to see Sundays as "relaxed" events, with Saturdays being the "serious" events. This gives teams who want to be super competitive a day, and reserves a place for entry players and people who want to do silly things in organized events (<3 Cake).
This would also lead to more one-off events running on Sundays with longer events running on Saturdays, giving people and teams something to do on Sundays if they miss sign-ups and want to start getting in on the action.
Of course in the down-time between big Saturday events it would be nice to see short or one-off 2v2 DM events run like the Saturday Box, to give "serious" players an event to keep in shape, so to speak.
Whether Sundays have 3v3, 2v2, deathmatch, capture point, racing, or whatever, I would like to see something start running on Sundays. Just my 2 cents.