Well I can't outright exclude Rock as a possibility, unless it's a redesign, I don't think he fits that standing up silhouette. There is too much around the shoulder area for it to be his jacket. I also don't think that DLC is how SNK would want to bring him into the KOF franchise if I'm to believe interviews that I have read. In fact Yasuyuki Oda said:
"I don't know why he's been absent for so many titles, but I remember that right after Garou: Mark of the Wolves came out and he got popular, the general feeling was "It'd be a shame to waste his inclusion in KoF right off the bat, so let's keep him out of this next one, at least.""
Based just on that I would say Rock is a no unless they are actually going through with a Garou 2 and including him in this game to build the hype. But I honestly would prefer someone else to be in the game because we already have Terry and Geese and Rock is just a mashup (a good one!) of the two.
Even though I do not always cry over a character not being in a game, when I do, I prefer to cry for Blue Mary.
Link to where I got the quote:
https://www.eventhubs.com/news/2017/jan/03/yamazaki-and-blue-mary-were-left-out-kof14-make-it-feel-more-kof-less-fatal-fury-art-fightings-jack-turner-john-crawley-also-considered/