Market research Asymco ( thinksApple could sell as many as 280 million iOS devices next year.

“Assuming that half the installed base upgrades every year and Apple adds devices required to reach the install base necessary (1.24b or 20% share) leads to the following unit sales projection (I’ve added 2008 through 2010 actuals and 2011 estimates based on my own current Q4 projections),” Horace Dediu writes for Asmyco. “This Approach yields an estimate of 225 million iOS devices to be sold in 2012.”