You'de be surprised. They may add additional areas, specific items, optional quests etc... all as payable DLC.
I just know that with Halo games the DLC was always additional areas. personally if they could do that every so-often with some cool side quest/story then I would be more than happy to fork over my 'hard-earned' money to them.
Q u o t e:
Sure they produced some doodoo games over 20 years ago