The company could facilitate a lot of content online, given that they already deal with just about every mainstream content provider around. Down the road, it seems likely that Comcast could even enter into direct competition with the likes of Netflix, offering Internet-only streams for a charge.
This also plays an interesting part in recurring concerns with ISPs and bandwidth caps. It is easy to see how the company could enforce bandwidth limits, but only for content “outside” their own network, effectively thwarting the competition. Comcast might never do that, but it certainly seems like a possibility.