The iPad Pro 12.9 is at it's one year anniversary. If it's not updated in March, then highly likely at the September 2017 Key Note.
My thoughts are the March KeyNote will debut the 7.9, and 10.1 iPad. Followed
By a Pro refresh for the 12.9 in September.
I hope in a silent update in the next few weeks.
A10x CPU, same DCI-P3 True Tone display, and same camera as 9.7 Pro model.
No need for a dedicate keynote.
I think it will be late 2017 before they update either iPad Pro.
Assuming they only update the Pro 12.9" in March, that will mean it will have gone for 16 months without an upgrade?!?!
I would be surprised to see that happen.