343 Industries Executive Producer Dan Ayoub told DigitalSpy that the team is looking at offering cosmetic microtransactions in Halo.
I think Halo certainly has the potiental for those kinds of things. We don’t have too much to talk about in terms of our plans down that line, but it’s certainly something… we’ve seen what the fans of Gears are enjoying, and if it’s something we think our community is going to enjoy, it’s something we’ll seriously talk about.
While the Halo series has sold map packs and cosmetic avatar items, they have not offered in-game microtransactions like the numerous weapon and character skins that Gears of War 3 and Gears of War: Judgment sell to players. Halo 4 currently has weapon skins as in-game unlockables.