The only thing that matters to me with the Elder Scrolls franchise is mods. If they temper with moddability of Elder Scrolls 6 (I.E., if somehow MS being the owner of the franchise means there's going to be no official tools to mod the game with) then - at least for me - it means the franchise is completely dead, period. And there's no other way to look at it. There's no way I would have played Skyrim past the 2013 or 2014 mark if it hadn't been for mods, same for Oblivion, and same for Morrowind. I don't bother with 'vanilla' Bethesda games since around Fallout 3.
However, if moddability isn't going to be affected, and if the PC version (at least) of ES6 will be just as moddable as Skyrim was, then this doesn't change anything for me at all and I'll still be able to enjoy another ES game for years after its release. And this potentially applies to the next Fallout game as well.
As for the other franchises, including DOOM, I couldn't care less even if I tried, no matter who owns them.