There's no doubt that iOS apps are bringing in more money now. However, the Android market shows you actual sales stats for apps and its clear that some people are making money on Android too. I also find it hard to believe that Android's current hardware sales volumes aren't going to eventually pull up market sales too. They may always lag behind Apple's but I'd be very surprised if the ratios stay as skewed as they are now.

If you're already established and successful in the iOS store then it makes sense to stay there. If you're starting from scratch then it's not quite so clear-cut, I think.