Right now SOTF is a total conversion mod so this will likely establish it as its own game mode. According to the patch notes there should also be performance improvement, better matchmaking, item rewards, and more.
For anyone that doesn't want to watch the stream or can't, they're showing off the Survival of the Fittest re-launch. I only saw a few minutes so I don't know if there was anything else. They also said it's releasing later today at least on PC, doesn't sound like it'll happen on Xbone right away.
Just so everyone knows, the new year event is only on official servers according to the steam notes.
Edit: Nevermmind, there's a console command to start the event on unofficial servers