Is Mortal Kombat 1 a continuation of the franchise, a pseudo-reboot, or a complete undoing of the events of the series, so far? If you ask Ed Boon, it's the latter.

The Mortal Kombat co-creator and CCO of NetherRealm Studio recently joined a "Kommunity Chat" after the game's official reveal where he talked more about the upcoming game, specifically, why it's named as such.
Boon explained the reason behind the name, saying:
Mortal Kombat 1 is the beginning of a universe. It is not a continuation of the Mortal Kombat 11 story so the characters have completely different roles in this new timeline and we really wanted to emphasize that with our title.
This is Mortal Kombat 1, it's a brand new beginning, you're going to be seeing these characters reintroduced with new roles, new relationships, and that's the main catalyst for it.
TLDR; it's definitely possible that Liu Kang becomes the corrupted god in this timeline.
This confirms that Mortal Kombat 1 isn't a remake of the original 1992 title and it doesn't necessarily make the events of Mortal Kombat 11: Aftermath canon.
Of course, it's not like NetherRealm Studios had a choice anyway. The studio had already used the Mortal Kombat name twice, so it was either Mortal Kombat 1 or it could use Mortal Kombat Origin, which is what an earlier leak proposed about the upcoming game.
In the end, all's well that ends well, or at least, that's what's likely the case.
Mortal Kombat 1 impressed in its reveal trailer and fans have been dying to find out if the leaked post-launch character list is true or not. The relatively small roster as per the available information is a sign that more are coming. But fans can't help themselves if they want to find out if Mortal Kombat 1 will bring back the relatively obscure characters from the less popular entries in the franchise, especially considering that it's introducing a new mechanic.
We're curious to find out just how different the characters we've come to love over the years will be in Mortal Kombat 1.
Is Raiden really just a plain old combatant with a rice farmer's hat? What about Scorpion and Sub-Zero? Are their families still feuding with each other? Is Sub-Zero technically still the villain of the two? More importantly, what is Johnny Cage doing taking part in a battle that supposedly takes place in the past? Will there be some form of time travel?
We'll find out the answers to these questions soon enough when Mortal Kombat 1 comes out on September 19 (or 16, if you have early access).
Mortal Kombat 1 isn't the only fighting game that's coming out this year. Street Fighter 6 and Tekken 8 are both slated to hit the store shelves within the next few months.