If by ‘solved’ you mean ‘never attempted except in scifi’, then sure.

I mean, sure, but this isn't "sci-fi" in the sense of a fusion ion engine or something. I don't think there are really any big engineering unknowns here, and building a rotating space station is certainly less technically complex than sending humans to Mars, and maybe even less than going back to the moon. We already know a lot about space stations from the ISS; it's just very expensive to build all the bits of a rotating station and to lift them into orbit.