I just hope to see more of the post-MK3 characters that didn't make the cut for MK9 and MKX for 1 reason or another, such as Fujin, Havik, Hotaru (alt costume as default, no flags), Reiko, Kira (perhaps she could replace Kano), Li Mei, Mavado.
The majority of the Trilogy characters have had 2 games to shine in, and not all of them need to come back.
Some of them can be rotated in for others that weren't in MKX, but I'd like the focus to be more on what happens after MKX (sort of an alternate Deception with Dark Raiden) and have other characters like Ferra Torr and Erron Black better fleshed out.