Yesterday at UDS Budapest, Canonical and Ubuntu developers laid out their plans for the Ubuntu Software Center in the near future. Among their plans are to make this "software store" more like that of Valve's Steam client.
Far down the pipe, Canonical wants to see more social integration with features like those found in Steam already: videos support, social network integration, built-in forums/community, etc. Coming up before that they have plans for WebLive integration, better performance, YouTube integration, ESRB ratings support, search improvements, and to make the interface more touch friendly.
More details can be found from the official session notes