According to 9to5Mac and TechCrunch, Apple would use the program to avoid at least some of the unpleasant surprises that sometimes accompany a software release’s first days in the wild. Apple has caught some flak in recent months from users disappointed in what many perceive as the software’s increasing number of bugs; a public beta may ease those complaints. Rumors also abound that iOS 9 and the next Mac OS X version will both focus on stability and performance, rather than new features.
The public beta may also extend to iOS 8.3, due sometime this summer; iOS 9 will presumably follow in the usual fall time frame reserved for iOS releases. The size of the beta is another open question—Apple doesn’t seem like the sort of company that would release an unfinished version of its software to millions of people, but stranger things have happened.