Well, there's the "D&D is dead" perspective, and there's the "D&D is dead to me!" perspective.
For the first perspective, I don't think D&D will ever die, truly. There will always be someone, somewhere, playing at least one edition of D&D in some format or another. There will always be a demand for RPGs--they are a unique pastime, a creative outlet that can't be found in any other format--and D&D will always be considered The One That Did It First. So no, I don't think it will ever "die."
But I can imagine a timeline where the developers have made so many changes I didn't want, and pushed it so far into a direction that doesn't appeal to me, that I no longer desire to play it. Other people will no doubt love the changes and new direction, and the game will thrive for years and years without me, though. This hypothetical situation would be my loss, not theirs.