Guerrilla Games, the developers of the Killzone series, are currently working on a new IP for the PlayStation 4. They've yet to actually reveal anything substantial about the game, but some hints have been made by a job listing on Guerrilla's website which suggests that it'll feature microtransactions:
- Developed micro-transactions and/or nontraditional recurring revenue models
- Have developed or supported online gaming communities or titles with a large ”social” focus"
This could indicate that the developer is looking at the free to play model. Of course it could also indicate that they simply want to integrate a lot of social aspects into the game, while offering cosmetic skins for weapons or something similar as microtransactions.