EDIT: Oops, accidentally said "in this post", when WoTC's announcement was in the FAQ that got leaked.
> Can I keep using OGL 1.0a to develop fifth edition content?
>
> No. OGL 1.0a only allows creators to use "authorized" versions of the OGL, which allows Wizards to determine which of its prior versions to continue to allow use of when we exercise our right to update the license. As part of rolling out OGL 2.0, we are deauthorizing OGL 1.0a from future use and deleting it from our website. This means OGL 1.0a can no longer be used to develop content for release.
https://www.youtube.com/watch?v=LTXkxy2KjXU