MonoTouch 4.9.0 is the first in a series of releases that will culminate with MonoTouch 5.0.
The 4.9.x series is tracking iOS 5. At the time of this writing, the API has been updated to iOS 5 Beta 5 and contains all the new features from MonoTouch 4.1.0, including USB debugging, the updated linker and better GC handling.
This release is available from the Alpha Channel in MonoDevelop.