I have an Austin-Healey Sprite(came to me and the wife in 1993). Do you think I've used AH original parts on it?
Speaker companies are not automotive companies. They are NOT required to keep a certain amount of "spare parts" around.
If you are that worried about buying a speaker and "never being able to fix it"...never buy speakers.
Only in the "rare occasion" do the original manufacturers, or outside companies, keep parts for old stuff around...
Klipsch still makes the Heritage line. Who knows for how long.
Regnar makes parts for the Dahlquist DQ10. Who knows for how much longer.
OHM is about the only manufacturer that keeps support for everything they've ever done...and mainly cause(except for cosmetics) nothing ever changes.