I think what's gonna happen is this...
MS is going to keep itself focused on gaming, the core will continue to support Live and it's downloadable contents, so long as the system supports them playing games, be it arcade classic, original downloadable games, or bigger titles. MS will probably continue to add in more support for other 'non-gaming' alternatives like movies, shows, and perhaps even sports?
Sony, I can assume, is going to work more on making their online services a conglomerate of media, less focus entirely on gaming and more on movies, music, and other things that Sony owns and can get ahold of easily, to put out onto their service. I picture it being more the technophile's playground, full of a larger variety of downloadables, but less of a focus on gaming as MS's ventures. (In other words, MS will work more on getting non-gaming content and spreading that section out, and Sony will be working more on getting gaming content, since they have more non-gaming.)
Nintendo will work towards getting a working online service together, which will probably allow for a lot of parental controls to help keep people getting into things they shouldn't be, and those that can or have the permission to, to do so. Being that Nintendo doesn't own much outside of the gaming business, their downloadable content will primarily be gaming, with a future focus on accessible DS demos, original content for download, and gaming online against friends and random people.
Speculatioooooon!