MindShift is reporting an explosive growth in education apps and presents some insights and recommendations for developers. However, the MindShift article only considers education apps for children. The education market is much larger and includes apps for all ages and abilities.
I believe the greatest opportunties are in higher education, particularly on tablets, where B2B rather than B2C might be more financially viable for developers. Tony Bates has some interesting thoughts on his blog where he thinks tablets will "become a regular component of teaching and learning in many institutions". Tony goes on to explain how tablets are more flexible, convenient and mobile than laptops, how tablet prices will continue to fall and how textbooks will increasingly become digital.
Tony also advises us to "build on the unique affordances of tablets, rather than merely moving material to a tablet". I tend to agree. It would be a waste if m-learning followed branded apps in offering static content that might as well have been placed on a web site.