I thinked it was hinted.
Yesterday some mentioned that characters were releasing by the end of 2017, but the only info I found was that they plan to release characters all the way through Winter (3 in summer, 3 in Fall, 3 in Winter), which technically goes up to early 2018.
The same articles mentioned that they plan to support the game "forever", which at most means an additional fighter pack or two.
Also more gear and skins I guess.
In the end, sales will tell. If DLC does well, they will add a few more since outside 2018's Game of the Year Edition of Injustice 2, they have nothing else from this team other than announcing MK11 for 2019.