As part of a recent Japanese Final Fantasy VII: Ever Crisis live stream, it has been revealed that the free-to-play mobile game will be coming to Steam sometime in the future. It's mentioned that the game is currently in development for the platform and that players will be able to share their data between the PC and mobile versions.
There has not been any mention of time frame relating to this Steam edition of the game, and likewise there has not been any word in regard to how the game will play in practice, but it does seem likely that the free-to-play nature with microtransactions will be preserved to maintain parity between the two editions.
If you have yet to check out Final Fantasy VII: Ever Crisis on your mobile device, you can head over here to read our review of the game and to see what we thought of it.