You cannot sell anything not OGL-based. So none of the WoTC material. That is what is happening now for Pathfinder 2 - now that official material is available the “free” material is going away.
No, that’s not what happened. The developer stopped and then Paizo stepped in. He’s not being prevented by Foundry or Paizo from continuing work on his converter. He’s decided not to do APs and adventures anymore because it’s turning into being too much like a job. He’s still going to be doing smaller stuff like modules. Paizo is now going to provide that missing content (and more, it sounds like), but they want paid for the job.
Foundry does not have a license from WoTC, so they cannot sell official materials. Do not confuse that with automating the rules.
You speculated about Foundry’s signing a license with WotC and ending the unofficial support that exists now. Again, that’s not how Foundry works. The unofficial support that’s available, which includes a
D&D Beyond importer, is all developed and hosted by third-parties. The Foundry devs could try blocking it on the official package list, but users would still be able to find it via third-party sites like
Foundry Hub or by installing directly from the manifest.
Even if WotC did decide to sell premium content on Foundry, I doubt Foundry itself would have anything to do with that.
Premium content is also developed and hosted by third parties. As far as I can tell from the
license, they don’t even take a cut. It’s very creator-friendly compared to e.g., mobile software ecosystems and the roll20 marketplace.