Of course, the App Store launched in 2008, so naturally we'd see a large increase. In fact, Asymco predicts that apps downloaded from the App Store will pass songs downloaded from the iTunes Store by March of 2011. The company made a similar prediction in September of 2010 expecting the event to happen by the end of 2010, which didn't happen, but it will happen, at some time.
After all, although most purchases for iDevice music is made at iTunes, not all are. Meanwhile, with the exception of jailbroken devices, all purchases for apps must be made at the App Store. In addition, apps will have reached 10 billion downloads in less than half the time it took for music from the iTunes Store (31 vs. 67 months).
Since Apple doesn't release numbers all that often, some of this is based on educated guesswork. Asymco estimates that 30 million apps are downloaded daily, but remember that as the number of iDevices increases daily, so do the number of apps. This number will just keep increasing.
Asymco also posits that as iDevice app consumption is increasing at such a high rate, it will soon overtake the PC software market (and based on the context, it sounds like they meant personal computer software, not PC = Windows, as is sometimes meant).
