I came across this. As far as I’m aware, this hadn’t been posted, but according to Mike Willette of Double Helix, the 2013 game was meant to be a continuation from the prior games.
Rare Gamer | The History of Killer Instinct – Retro Gamer Interviews Chris Tilston, Kevin Bayliss & Mike Willette
A shame they hadn’t been allowed to continue. It makes me wonder how the game would have turned out had it been that DH hadn’t been bought out by Amazon, or what would have happened had it been that Iron Galaxy had developed Season One in the first place.