I think it is a "decoy" rumour : scattered around by NRS to make sure people will play more others characters, that , in the past, were unpopular, and this way, players now have chance to enjoy more all overall work they did hard in this game and put in each character individuality .... but, since they (NRS) put a lot of "heart and effort" to bring back our beloved old school MK characters back, renewed and updated, I don't think they will dare to **** off the franchise, doing a very stupid move like this, just cutting out 5 characters well-known .....
Maybe if they (NRS) are stupid and idiot enough to do it, let's say, there is always possibility to bring back in other sequels, characters that are "hibernating" during a current game .... this new MK 2011 is incredible, all characters are cool in this new engine, could be a shame just leave any of them behind .... specially ,for example, let's say, Stryker, who finally deserves some proper respect for being portraited as a badass, and having a pretty cool designing look.
Or in the worst scenario/situation, since the franchise have more characters post UMK3, I think next game will be the turn of others, like Tanya, Rain, Sareena, etc .... maybe , mixed with some characters of this MK 2011 ....
I hope Skarlett, by now a DLC (MK 2011), has more importance in the next game, and make part of story mode as playable, if MK2 sequel will have one ....