Content already released is not the same being able to release new content under 1.0a. They might try and force all new content to be under the new OGL. The issue is they are tapped out of good will from the community and have shown themselves to use weasel words. So all press releases from them should not be given any benefit of the doubt.
> 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.
Content already released, yes. The post says nothing about being able to make new things under 1.0a, which is where a lot of the nervousness comes in for people.
Sure, but "not being explicit" is very different than the way OP phrased it ("WoTC says in this post") -- it made me think I'd missed some explicit mention of it.
FWIW, I don't even believe they ever wanted to try to claw back e.g. the 3.5 SRD, so I'm not as concerned as other folk here. (But it's also clear that if they have no such intent, they'd need to make it legally binding for folk to trust them.)