I'd like to bump this to add an idea, and I'm doing it at the dead time of the morning so it can be buried if no one really cares:
I believe I did a thread similar to this where we discussed Tape format remaining in place without the Digital revolution, or analog never being replaced by digital, or something like that.
From the discussions there, I think a good way to have Vinyl remain would be to skips the CD age altogether and go straight to Digital Downloads. Because with an MP3 or MP4 or any digital type you'd like to have it (or whatever type they could have it be in the 80s), you have no need for a CD. That's what's happening now; CDs don't really matter anymore, and vinyl is rising as a result because people like to be able to physically handle music, and vinyl makes them feel like they're really experiencing music by having this big LP and album sleeve and turntable to play it on. And, on top of that, it's becoming a thing where with a vinyl album, they give you a code for a free digital download of the album. So perhaps that could arise earlier: vinyl LP's released, with a code to a digital download version of that album or single.
There's two ways such a scenario could work: one, digital technology is progressed in the 80s enough to where digital music downloads from an internet-type body is possible, and some sort of container exists which can store that data in reasonably high amounts. Two, CD is retarded either in development or popular adoption to the point where when they could take off, we've already made it to the point where digital downloading and data storage on portable music players are possible; and it doesn't even need to be portable, since digital could be at home and then cassette's could still be used for portable listening until such time as a portable digital device is invented.