How many will listen to tape and vinyl in the next century?

There is still a lot of good original pressings around from 50s, 60s and 70s. Many of them held up remarkably well, but I don't know about 100 years more,  enough of them will probably deteriorate. In a hundred years playing records let alone tapes, if there are any tapes, may become sort of a strange elite, even aristocratic, hobby. Better than nothing.

And thats the worry, the shortage of good LPs.

Tonykay, right about Willy. Six years ago he aligned and calibrated my 682ZX extermely well. Going to send the deck to him this year again to have it in perfect order for the next five-seven years.
As for the next century..well, someone got to replace him. And us.
I do sound optimistic, don't I?