It is too late for it to happen this year based on the prior duration of such efforts.
Remember that the challenge was a means to attract more people into the program, not a long-term play. Between the corporate contracts, prior year challenges, a maturing business-traveler focused network and the CC-based options it is completely reasonable to believe that JetBlue found out it has the right number of members reaching the Mosaic tier these days and no longer needs the challenge.