I think they are going to make more revenue, eventually they might even reach 1 billion in profits. The trend is more games being sold via xbox live, the next xbox (yes there will be one) might offer a service like steam does on the pc. Onlive probably flops and with a steam like service you would still own the games and could play them offline.
Untill then, the popularity of xbla will grow, the originals will decrease in sales but the most growth will be seen in the dlc department. GTA4 is one of the first good examples how DLC should be handled and more games will follow that example. (just notice how much companies like lionhood/bethesda/bioware are talking about DLC, besides that map packs for fps games are standard and sell extremely well).
GTA4 alone will be a big part of the cake. Total DLC sales will probably reach 3/4 million (with the next DLC included), thats 60 to 90 million alone. One games gives you almost 1/10 of the annual expected revenue. I know there wont be games like GTA4 every year, but DLC will be important for every blockbuster game, gamers will expect DLC and they want to pay for it, if it offers enough for their money.











