Not sure what you're asking. Do you want to know if you can keep playing MW3 while everyone else is playing Black Ops 2? If so, then yes you can. You can still go online and play MW, MW 2, MW 3, Black Ops and World at War. The problem is, support has for the most part been dropped and the hackers have mostly taken over. So getting into a good game is a little tougher because of the cheaters.
MW3 still has quite an active online seen even with BO2's launch. not sure about the others. console gaming isn't as affected by the "cheaters" as the PC community but it still happens from time to time, as what happened with COD4. but as for the support. you would need to stay with the current crowd to get that, activision only looks after those that give them money.