Is mobile app growth over-hyped?

There are numerous statistics on the growth of mobile apps in the various stores, and also about the number of downloads. Apple claims over 500,000 apps in its store and Google claims over 450,000 (this time last year it had only 150,000). The number of apps, downloads and rate of growth is phenomenal. 

Is this just a temporary fever or will this growth continue, and if so what will drive it?