According to a Steam registry on Open Steam Works, Gotham City Imposters will be in some way be going free-to-play as noted by the "Gotham City Imposters F2P Trailer".
This change isn't particularly surprising as it was already free for PlayStation Plus subscribers and given that the comic multiplayer shooter already has microtransactions in place within the unlock menus.
Of course, those who already paid $15 to play the title (or "beta" as some would call it) will likely feel slighted by this change, as many feel that the free-to-play model should have been the way to go in the first place.
While this seemingly confirms the free-to-play model for Steam, it still leaves the Xbox 360 and PS3 versions in question. The introduction of the first free-to-play title on Xbox Live, Happy Wars, opens the possibility for an Xbox Live F2P version at the very least.