Searching for "Midi" in the Sonar updates page gives the following:
September 2015: Synth Recording
April 2015: Better Drum Maps (Soloing), New MIDI Engine
March 2015: Onscreen Virtual Controller
January 2015: Pattern Tool, MIDI Enhancements, PRV Enhancements
That's really not much after the initial release, and nothing in 2016. But then, what would be needed? A better drum map editor and improvements for staff view (triplets, staccato, and several other) would come to my mind. After all, midi is a pretty old standard and midi editing is well supported in Sonar.