If EA has another Jam title coming up (maybe Q2 to coincide with the playoffs), I doubt they will do a roster update. If EA is not making any money from the game via DLC and/ or making new DLC to offer, I doubt they will do an update. In short, I doubt they will do an update - my guess is there are licensing issues, there is no real incentive (i.e. they are not making money on the DLC), and more than likely, the development team has probably already moved on to whatever is next.
NA Jam is most likely dead in the eyes of EA, which is why it was offered to PS+ subscribers. Offering it now is a good last chance to get some $ for DLC before the servers are shut down.
This approach is really good for the publishers - one last chance to make money, or get the game in the hands of folks before the next version is released (i.e. see BioShock 2).