So after some reading and rewatching the trailer. It seems they will try to do Injustice "Multiverse" mode. Just in this case it will be timelines. Raiden fighting present Scorpion, and after he kills him, a MK3 one comes out.
That also is supported by the scene showing a woman standing next to the hourglass. Hourglass = time.
I guess that's how they plan on bringing classic characters (I mean at this point, we would be lying to ourselves if we thought, that they didn't bring the OG chars in as well).
So this entire timeline thing, might be a sign of NRS/WB embracing SF tactic of doing seasons. It makes money, and they know it. So most likely they will be dropping new chars with every new season.
After all if I remember correctly, they did mention in the past, how they wanted to make MKX into a long lasting platform, instead of just making a sequel. So MK11 in this case could be that long term platform they had in mind.
Not to mention, from business point of view it makes sense. Why keep investing into new sequels every 1-2 years, if you can just do "live service" and keep the game running for 4-5 years.
Not only you save on costs, but also they can earn quite a lot from costumes, char packs.