Sure, they can retcon it whenever they want, but for now they are dead unless officially stated otherwise. Which honestly, I wouldn't mind at all since Chris is who I main in all dream matches.
Like I said though, the comments I referred to were said on the OFFICIAL KOF 10th anniversary page, 5 years ago. The usual rules of engagement are that "Word of God" trumps all, right? That goes even beyond what the games present (which are usually ambivalent until they try to make sense of things some games later, any way).
So, in short, clinging to what may have been the "old explanation" (2K's strikers seems to be the main one) is not really the standard now, it seems.
Speaking of the New Faces, did they ever say if what is sealed is only Orochi's spirit or Chris' body too? However, I don't see how the New Faces evaded that, Yashiro pretty much rips off all of their throats in their own ending, and then there's their 2k strikers. Also, Geese depends on which continuity you are 
Well, on one hand, I don't think it was explicitly said one way or the other about Orochi's sealing. But on the other, it's pretty plain to see that the New Faces' own storyline and ending didn't happen as was depicted, just like what could be said for a number of the other endings that were presented in that game.
After all, there wasn't any opportunity for Shingo+Kyo's ending to occur like it did, because Kyo and Iori were supposed to have disappeared following the events of the "Shingi Trioca" (Heavenly Treasures) ending, which was definitely the one, true ending of that game.
Everything points to the notion that, as far as SNK is concerned, they just want to keep as many fan faves around as much as possible, without having to worry about fairly insignificant things, like storyline, stopping them.
In other words, now that they've actually gone through the trouble of crafting Mature's sprite set for this new generation of KOF, expect her to stay around for a while. They may go into depth to try and explain how she and Vice survived, but I wouldn't be surprised if they didn't. Because again, they now have the "word of God" fallacy to rely on, which basically gives them free reign to bring back any and all KOF favorites, as they wish.