Analyst Charlie Wolf at Needham & Co. says that Android is losing ground to iOS in the US. Currently, Android is the leading smartphone platform in the states, but is gradually losing share, at least that's what data frmo IDC shows (via 9to5mac).
In the first Quarter of 2011, Android phones had a 49.5 percent marketshare while Apple's iOS had 29.5 percent. However, in the previous quarter, Android had 52.4 percent, and Apple was just below 20 percent marketshare. Still, these numbers seem to fluctuate. However, it's said that the iPhone 5 will shoot iOS marketshare up, as it will be available on both carriers (AT&T and Verizon) at launch.
They also say that it's possible for the iPhone 5 to launch on both Sprint and T-Mobile, which would give it even more marketshare.