Almost every one has a mobile here, even some of the poorest people. The reason for that is the dirt cheap handsets combined with lifetime connections, you can get a handset for $28 plus a life-time connection for $12 and you are connected for life. I really don't see this people buying $300 smart phones and start using Google or buying stuff from internet. It is not going to happen and when i see this huge companies talking about how they will make tons of money from China and India, it only makes me laugh. Again just have to wait and watch.
But it's going to be a process that will take more than 5 years. When they have a GDP per capita of $40k, they'll be worth a hell of a lot to whichever search engines they use.
But even then, the growth won't be attributable so much to mobile (even though it may come through that channel) as to developing nations.