The current state of play would suggest that the 5E SRD ceases to become Open Content under the OGL 1.0a and instead is content covered by the "OGL" 1.1 (which is not open) and why on earth would they pull the Basic Rules? That is marketing.
My prediction is that the 5E SRD and Basic Rules will no longer be freely available
after One D&D is released. You're correct that it makes no sense to remove them now, before they have a new ruleset to replace them; also, the leaked OGL 1.1 draft explicitly references the 5E SRD.
However, I assume that in 2024 they'll update OGL 1.1 again (OGL 1.2?) to replace those references with whatever One D&D's SRD equivalent is. And then remove free access to the obsolete 5E rules from their web site (and possibly D&D Beyond as well, except as Legacy Content).
I also wouldn't bet on any publicly available One D&D SRD or Basic Rules; those will be strictly on D&D Beyond and only accessible to subscribers.
No PDFs that seems to be a WoTC thing has been for a very long time. At least no pdfs of current material.
Definitely no PDFs of One D&D material, agreed. And yes, it's more likely they'll just leave 5E rules solely accessible to D&D Beyond subscribers. But there is a tiny chance we'll see 5E PDFs on DM Guild. (Very, very tiny.) Assuming they're still in the market of selling PDFs of their older-edition material at all by 2024; they may decide it's no longer of value to the brand.
I do not understand your last sentence.
Putting it more simply: they could potentially use OGL 1.1 to shut down OGL 1.0 sites like the Hypertext d20 SRD, or at least make the attempt. But we don't know for sure yet.