If so, have I ever got an answer for you! I was fortunate enough to grow up on computers in the late 80s and beyond.
How many 'web apps' did I use pre-broadband? Zero. How many desktop apps did I use? Well, I don't know, but it was a lot. A lot more than now.
So the future is here -- we're already past the point of web apps being more common place than desktop apps, sans browser. Since we're already past the point where your original question has meaning, take a look at the desktop apps that surround you today and tell us what cannot be replaced and why.
We can see cloud-based AA/AAA gaming is largely a failure for now, as a very easy example. And of course, all of that infrastructure and software that runs those websites is native to some degree.
Regarding what is wise/not wise to learn. Do what feels right and what makes you happy today. You like webdev and the framework-on-framework-on-framework-on-framework-on-dom-on-jit development? Go for it! You like iOS development? Do that.
You can make money either way and earn a comfortable living with experience. The market is wider for "webdev" (too broad of a term encompassing too many technologies) than it is iOS. Your generic run of the mill company may need a webdev, but far fewer are going to need an iOS dev.
If your goal is money and to screw the rest of life and relationships, just look at job postings today and see what the rate is.
Anyway, you're (probably) too young to worry about "what about 10, 20, 30 years from now?" questions. When I was young the Internet didn't seem much more than Compuserve, AOL, and refdesk.com. Could I have predicted that the web would be what it is today? Absolutely not :-)