Bummer!
Years ago I was reading a book about the Beatles and it had a section on valuable collectables. We had a bunch of them!
I could see first edition books having a much smaller, but more rabid audience. Harder to find a buyer and condition has to be there, but museums will want to have some books in their collections to show off 
Vintage guitars, electric and acoustic, are already up in value if you have the right ones. There has been a down trend in the market due to the economy but it is picking back up again. Now, will they still be collectible in 100 years? I think so - I suspect much less current-for-2115 music will be made on guitar; much more likely to be the current-generation iPad jacked right into your brain or something. But just like with old violins and other old instruments, there will still be folks who still actually “play instruments” and some guitars will still represent the best examples within that context. With acoustic flattops, the stress put on the top due to string tension always threads to make the guitar implode and there have been fears that guitars will eventually become unplayable over time, but so far that hasn’t panned out with old-but-maintained Martins and Gibsons from the 20’s and 30’s…