The advantages of tubes vs. trying to achieve the same things with FETs are pretty big for guitar applications. Hi-Fi is arguable, but a lot of it is really "vibe" related rather than technical, and tubes have great vibe so they're pretty ideal there too.
I don't think it's going to go anywhere, and I don't think tube supply is going to dry up. If anything I would expect increased sales and that key general purpose tubes like the 12AX7 and 6L6GC eventually end up being manufactured in the US again.