Browsers have graduated from a simple tool into a platform. For example, Mozilla Firefox has a build in database (starting with v3), support for plugins/add-ons. With appropriate add-on installed, Mozilla becomes a web browser, chat/IM client, VoIP client, RSS Reader, email client etc etc.
At present, various browser components (add-ons, plugins) and web services exists are disconnected entities. If these can be integrated, browser can be the window to the Wide Web World! Flock is trying do it, but still the components are held very loosely. Interaction between various browser components has to be seem less and the browser (through web services) should be able to react to user needs more intelligently.
The video posted below is a glimpse of what next browser might look like.