According to Gartner, in 2013, the number of smart devices in use world wide will eclipse one billion. That is a huge number. That represent something like 15% of the earths population. But actually, the number of devices sold isn't a one to one relation. For instance, I have several devices, and I would assume many others have several devices.
There is one fact that companies just cant escape, if they have a major online presence, it needs to be optimized for a mobile experience, or you will lose business. It's not a matter of maybe any more, it's a fact.