I'd say this is 99% of a win. The one thing it does still leave is the claim they can de-authorize 1.0a at will later. For active products this is not a problem

I'd say this is 99% of a win. The one thing it does still leave is the claim they can de-authorize 1.0a at will later. For active products this is not a problem, as CC BY is a strictly more permissive license and they just move to claiming they're using the CC license. However, for second-order derivatives there is still one problem. 1. Third Party A uses OGL 1.0a content from Wizards, licenses its own work as OGL 1.0a as a result 2. Later Third Party A goes out of business 3. Third Party B reused Third Party A's content under OGL 1.0a. 4. There's no one left to relicense Third Party A's content under CC BY. But "don't make second order derivatives of abandonware content" is a lot easier to work around than "don't make stuff compatible with the large existing ecosystem"