Well, right now the apps market is great and will probably keep going on for quite a long time.
I believe it all depends on your product, if you release something that is amazing then it is possible that you will hit the jackpot, no matter in what platform you released it. For mobile devices you got to know how to monetize it as for mobiles you cannot really sell for a high price, however if you got millions of micro transactions you got it! it all comes down to the quality of the product in my opinion it got to have an x factor, whatever it is.
As when it comes to the traditional desktop market, I don't believe that the market will dry up at all. unless you get to a point where all you need is a tablet or mobile device to do everything efficiently.