1st Activision dont make games they promote them. and treyarch have agreed that this is their last call of duty game cos they knows cod5 is an epic failure.
So infinity ward are who you meant Untouchable Gangster. they make the best ones. but i think this COD6 or whatever it will be called will be the last one. Otherwise i think they will over do it. they could of stopped at cod4 really but if they make a better one than cod4 they should stop there.
Correct, Activision do promote games, but thats part of a larger job role. They publish games - issuing contracts to development houses like IW (The contract include a detailed description of what type of game they want, as well as working titles and scope for sequals) who will then design and pitch their ideas to the publisher.
I have no idea how many will be made in the series...safe to say that CO

MW2 is the only one confirmed or rumored but the contract signed by IW and Activision may say that another one will be made. The whole reason W@W was made was that Treyarch had signed a contract for 2 games in the COD series when they made COD3.