Last I heard from then, RTD was struggling financially. Hosting isn't really free, you know -- nor is administering a site like that :-). The PSF should offer to cover their costs for hosting the Python docs, which I presume are pretty dang popular compared to many other things currently hosted at RTD -- the peps and devguide won't cause any load in comparison.
I've brought it up with Eric Holscher before and he's said he doesn't want any open source project to feel like they have to pay. That being said I would ask the PSF to be a sponsor of some form if we did move all the docs over (for the devguide I'm not worried about the increased traffic). I've also suggested to Eric to apply for a PSF grant to move the docs over to Read the Docs so he can get paid to help make sure any such migration would be done well.
-Brett