What 26er parts did you meant? Wheels and forks? Sure it’s not as available as other sizes but it’s still there and much cheaper then it was ever before. And how many wheels or forks a rider need? It should last for many seasons to come.
For those who travel abroad to ride a bike, 26 is still a best bet due to availability of tubes and tires virtually anywhere.
No, 26 isn’t dead. Won’t be in the forseeable future.
I ride my 26 – a lot – and my 29. A lot. The 26″ bike is very nimble, I tend to ride 29 on longer rides. And 27.5 is touted as the ‘best of both worlds’, but it isn’t really. It’s a great bike, special in it’s own way. I’m lucky enough to have a bunch of different bikes. I’ve heard of “1 frame size to rule them all”, but that’s just not happening in the real world that we live in.