You know... thinking about it now, it sort of makes sense that an SNK rep (specifically from KoF) would be among the DLC Fighters. I remembered back in the Direct were Sakurai spoke about Ultimate's new mechanics, and among them was the ability to "short hop". Short hop is one of the movement options seen in KoF games (ah yes, playing through the KoF XIII tutorials).
And another thing, I checked out that tweet linked earlier and, one
response SERIOUSLY got my attention. If this line is supposed to be a blatant hint to who fighter #5 is, I dare say... is it Goemon?!
IS IT TIME?!?!?!
EDIT: Forgot to say, Impact within the Ganbare Goemon games is the giant robot that kinda looks like Goemon thus, would be a good (obvious) hint.