I was talking with one of my players who's been keeping up the most with the OGL saga about what our ideal post-5E system would look like, and unfortunately, it would have to look a lot like 5E, which is the compromise choice between the folks who want a much lighter game than 3E and the folks who want to have lots of player choices in character development.
There aren't any OSR games that can be built up without a lot of work and even Pathfinder 2 looks too crunchy for a bunch of our players.
So our best bet is for an SRD published under ORC that allows Kobold Press to continue producing 5E supplements. Once we have a framework similar to what we have now, including subclasses and advantage/disadvantage, we might build or modify that chassis to better suit our tastes.
If I wasn't actually running a campaign now, I would consider taking Castles & Crusades out to the garage and trying to 5E-ify it, but that's too work for me at the moment at a time when I'm unlikely to switch over my two ongoing play by post games to a new system, not to mention my Discord and live games.
I do look forward to seeing what this new era of D&D clones produces, though, and would happily buy one that works for me and mine.