I think Blu-ray is around for a while but I think it's the last mass market optical format. The on-line services are currently limited by bandwidth but I think your view on how long Blu-ray survives and how quickly bandwidth improves should probably be pretty heavily linked.
I see nothing wrong with Blu-ray being used for your TV, and not at all for your computer.
I agree that one day bandwidth may be great enough to supersede Blu-ray, and I agree bandwidth improvements are tied to the end of Blu-ray. However, as Blu-ray offers 36Mbps data rate, that time is certainly not now.
Oh, and if the oft-dreamt-of switch to 4K in the living room happens, that time will be pushed even further out. You might even see one more format.
VHS to DVD was a massive jump that was an improvement for anyone. DVD to HD / Bluray is certainly an improvement but I know a lot of people who have been pretty lukewarm about it because while DVD isn't as good, it's good enough for them (certainly given the price differential).
I wonder if Bluray to something else will suffer the same problem amplified - an improvement but not one that many people are willing to put their hand in their pockets for. Yes I'm sure there's some market for it among home cinema fans but is it enough to make it viable? Or will most people be happy just streaming 1080p?