By Ryan Kim, GigaOMIndependent, off-deck, app stores will become the major driver of mobile app downloads by 2015, eclipsing on-deck app store. That’s the word of a new report from research firm MarketsandMarkets, which forecasts the growth of the mobile app market. The report estimates the global market will be worth $25 billion by 2015, with Apple’s App Store accounting for 20.5 percent of total revenues. While on-deck stores like Android Market and the App Store represent 3/4 of app revenues, off-deck application downloads are expected to grow faster through independent stores like GetJar and others and will ultimately eclipse on-deck stores by 2015. This is consistent with another report by Chetan Sharma Consulting last year, which forecast that off-deck mobile app sales will eclipse on-deck, operator-managed mobile app sales by 2012. That report was commissioned by GetJar, but the latest forecast by MarketsandMarkets validates that conclusion. If this holds true, it suggests developers will have to embrace the increasing complexity of multiple app markets. Amazon, for example, recently launched a new app market for Android, joining other markets from carriers such as Verizon Wireless. While it may mean more work updating multiple apps in various stores, the payoff may be greater for developers willing to wade into various app stores. And as the numbers show, Apple’s dominance in app revenues will subside over time as competing platforms mature into solid revenue makers for app developers. That’s another reason for app developers to look at all their options. Overall, the consistent theme out of the latest MarketsandMarkets report is that the app revolution is real and only getting bigger. With the Apple App Store hitting 300,000 apps and poised to hit 10 billion downloads, the overall market for apps has shown remarkable growth in the past few years. MarketsandMarkets estimates that mobile apps generated $6.8 billion revenue in 2010 and is expected to grow by 29.6 percent between 2009 and 2014. The research firm said mobile app downloads grew by 146 percent in 2008 to 1 billion, then jumped to 6.4 billion downloads in 2009. The biggest market for revenue is North America, which had 41.6 percent share in 2009. Asia, however, is the largest market for downloads, while the European market is expected to become the largest market for downloads by 2015.