With the Google toolbar being given new life by Google promoting it for the purpose of tracking your web history, I fully expect the toolbar to start taking a more prominent place.
Popularity is now expressed in PageRank only. Soon when visiting a site you'll be able to see how many people bookmarked it on Google Bookmarks and how many subscribers Google Reader has for the site's feed. They would shoot themselves in the foot if they would start to report on how many visitors that site has had in the last X days/months...
Google Highlighter currently highlights search terms. Look for integration with Google Notebooks: highlight and annotate any web page.
Content creation via the toolbar is already made simple when it comes to Blogger and Gmail. Docs & Spreadsheets will follow as will Picasa and YouTube.
Note This will work right from the toolbar itself.
Google Talk will optionally be available via the toolbar. You'll be able to have it popup a message window but short texts can easily be displayed in the toolbar itself. "Honey, don't forget to buy milk on the way home". A status dropdown including custom states will make Google the ubiquitous Twitter.
Similar Pages will eventually start to work like the Alexa related pages: it will suggest pages from the same category, same quality. Possibly the toolbar will show an Amazonian "People who visited this page also liked..." kind of message.
Indexing your information will become easier with the toolbar. Anything dropped on the browser will, optionally, become indexable. Your (G)mail is already indexed. Your Docs & Spreadsheets are. Your Google Reader. Your Google Bookmarks. Your Web History. The last step in making Google the central hub of your memory retrieval setup is to make indexing your own content easier and more mobile than installing and running the Desktop Search.