what I'd love is if WotC just went ahead and did a whopping big space opera setting, that was designed using the 5th ed rules and such, but was in no way balanced in any way against anything in the D&D settings. Yes, you still need the player's handbook, or at least the basic rules, but everything in the space opera book is very much its own creature. attributes and savings throws work the same, as do skill checks. Humans aren't that different, but classes, weapons, and everything else is all new.
It would still be sold under the D&D umbrella, but that is only because of the rules system.
then a couple years later, maybe do a pulp game or modern era, or supers.