There are at least 3 major free-to-play fighting games released or on the immediate horizon (4 if Soulcalibur: Lost Swords counts), with each taking slightly different approaches, since each serves a different purpose. Tekken Revolution is built around Facebook-style timed gameplay and progressive stat building to encourage microtransactions in order to keep playing and keep up; Dead or Alive 5 Ultimate: Core Fighters isn’t much more than a playable demo with the option for upgrades toward the full game. Revolution, cash grab or no, is there to serve as a first step for new players interested in the series before taking the plunge on either of the current full releases. Core Fighters seems more like they realized people were willing to buy the tragic Ninja Gaiden 3 just to get their hands on a Dead or Alive 5 demo, so why not run with that? The new Killer Instinct looks like more of the same, though with a much heavier emphasis on the free-to-play aspect, probably to show off that the XBOX One is fully capable of free-to-play games.
In the future there will be many more free-to-play fighting games, just as there are many more free-to-play games in most other genres, especially non-AAA multiplayer titles, of which fighting games are a prime example. And, yes, I know there have been free-to-play fighting games before, or at least free-to-play games in the same vein, but none were the work of major developers or belonged to major franchises. But what does that actually mean for the players?