Gee, maybe we should try to finish that OGL Shadow World Atlas after all...
As someone who likes and is playing* D&D 5E, please don't. First, it is not OGL/D20, not at all, so they won't be compatable and second, while I am sure there are D20/OGL hold-outs (like there are RM2 hold-outs), I don't think this would generate any serious response by the D20 community. Of course, I could be wrong about that, but I don't think so. And, a totally unrelated reason, I think it would be down-right criminal to sully SW with the OGL - but that is totally unrelated, of course. (OK, to be perfectly fair, it might generate new traffic to SW, and perhaps even RM, just not sure how much.)
*This after being sure I would not play/like D&D again because of 3rd and 4th editions, especially 4th edition. Of course, as an RM lover, there are still things about it that I would like to change and would do differently in any 5E game I ran...