iOS 9.2.1 Will Be Small
Developers and beta testers are starting to provide some feedback about the contents of the iOS 9.2.1 beta 2 and if you were expecting a huge change from iOS 9.2.1 beta 1, you're going to be disappointed.
As of right now, the iOS 9.2.1 beta 2 doesn't appear to be much different than the first iOS 9.2.1 update that Apple released during the tail end of 2015. Beta testers have been unable to find any significant changes in the new beta outside of some bug fixes.
Barring a major change, it's looking like iOS 9.2.1 will be a small incremental update that's focused on fixing lingering iOS 9 problems.
MacRumors believes that the update might come with a fix for Mobile Device Management issues that came with the iOS 9.2 update. Apple outlines this iOS 9.2 problem on its website and mentions that it will be delivering a fix in the near future.