20-Year Prospect
It seems unlikely that photography, as an artistic medium, is going anywhere in the coming decades. It's true that technology can greatly change the way we interact with photography—the "Live Photos" feature on new iPhones being case-in-point—but it's unlikely that photos will go the way of the 8-track anytime soon.
So long as photography remains a uniquely expressive medium, aspiring photographers should continue to be as ubiquitous as struggling writers or would-be actors and actresses.
Still, that doesn't exactly bode well as a career prospect. As we've been saying throughout, the outlook for a career in photography isn't great. But as we've also said all along, there's no reason to not give it a shot if you think you have the skills and passion to produce professional-level work. It'll take determination and dedication, but get started early and make sure you never stop trying to improve your work.
And if the whole high-culture artsy thing isn't for you, then you should still be able to find work commercially as well—there's certainly lots of potential there for change as new technologies emerge.