This post is going to reference the incoming subscription-based service "Call of Duty: Elit3," by Activision, and to get this out of the way - despite the title, this is not simply reactionary. There are any number of complaints to make, and while I did go for the cheap and easy "milking a franchise" joke in the title, there's more to look at here.
Basically, "Elite" (for the time being, I'll eschew the leet-speak spelling) is a multiplayer management service (similar to Blizzard's Battle.net), except that it offers "premium" content for a paid subscription. Depending on your point of view - glass-half-full or glass-half-empty - this is either a way to charge for things that may have already been available free or it's a way to offer more content consistently.
There are a number of concerns that could be raised here. First of all, the obligatory "you can play free too" line is there, which has often signaled the tacit "...but you won't ever be able to play on the same level." The possibility of charging more for less is another potential concern - with the paradigm already existing that map packs for these games come out, they could still come out this way and this could just be a charge on top of a charge.
However, I think that - with the goal of being optimistic - there is a great opportunity here from a production standpoint. If the paradigm changes to one where all the new content is folded into this monthly "premium" charge (the same way MMO content is often added), it could provide for a state where it is more justifiable to keep a team working on addon content, since there would be a steady revenue stream.
Ultimately, this could be better for the end user (provided, of course, they opt-in to paying), but it is obviously an experiment. I can think of few better platforms (that is, the Call of Duty series and its massive user-base) to effectively pilot this test, though.