I haven't heard any plans for monetizing Battle.net 2. Largely, this is the first I've heard of it.
Personally, I'd not be surprised if Blizzard simply went for the 15/month subscription basis for all of their games, one subscription fitting one game or all of their games depending on how much Blizzard you play being up to you.
Games would be handled on a per-content-chunk basis. So of course you need to shell out for SC2.1-3, Diablo III, but then you get in-game content upgrades and superior Blizzard customer care.
So far, I've seen minimal* changes to WoW since Activision came out.
------------------------------------------------------------------------
Just a quick off-the-cuff statement: It's always awkward to me when I call someone out in CGA. For the record, while I'm challenging RyanB in this thread, I quite enjoy his presence in CGA and think he's a great guy.
*Changes I've noticed since Actiblizzard started up:
1. Models for items seem to get copied more. This could be because a) Activision cut a lot of the modeling department staff, b) HD models, which they are using, take a lot more time to make, or c) The modeling team is going hard-core for Cataclysm and 'that new MMO.'
2. Activision created a team focusing on the social and UI aspect of WoW. This team is responsible for a huge number of upgrades to the UI of WoW, including more mailboxes, in-game quest support, the cool new Dungeon finder, and little upgrades like clam-stacking and increasing the size of leather or potion stacks. It's basically a "what do players want" team.
In addition, this team is dedicated to overhauling a lot of the old WoW systems that have been around since forever, such as the new guild system opening up in Cataclysm.
3. Advertisements. Whether you hate or love Mr.T in WoW, that's Activision.
4. There does seem to be a bit more of a push towards deadlines than before, but Blizzard is still pretty lax about deadlining. And that's a good thing.
--------------------------------------------------------------------------
Now, I should mention that I do realize that I have a huge amount of Blizzard loyalty, so I might be blind to the facts

But I don't give my game loyalty easily. I've seen my share of great companies turn into greedy bloatware factories.
I don't see that happening with Blizzard, but I could be dead wrong.