The newly-announced Killer Instinct for Xbox One is apparently embracing the free-to-play model. It's a digital-only release, and includes just one character to start. The rest, you'll have to pay for.
IGN reports that Jago is the free character on launch day, and the game will offer returning and new characters for a price. That cost is undetermined, for the time being. If the price is steep, we can probably expect to see quite a bit of Jago vs Jago matches online.