really happy to see this. mk9 is by far the best mk ever made so, in the case of mk10 I'd want:
the team on the same track. 2D fighting, don't ruin it again with 3D or weapons and shit like that. have all the fighters till MK3 (even if the new story mode keeps some of them dead, they're all great characters and should be in the game even if it's unlocking them as a bonus), obviously make at least 6-7 new characters that are good like Skarlet and not crap like Hsu Hao or something (wouldn't want guest ones either), "fix" some things that should have been in mk9, as in, access to all skins (even more new skins if that's possible), not sloppy work on DLC characters like no alternates or an entry line, cyber Smoke even as a bonus if Smoke is kept human and overall reinforce the game more (maybe two xray attacks, more moves etc).
in the case of UMK9 I'd want again the above reinforcements of the game, I guess the story wouldn't be expanded or maybe they'd just add some bonus chapters for the DLC characters that will be an introduction to their role in mk10.
overall, even if it's an early release of something new, as long as they are on the right track with mk I'd get any game after mk9.