For instance, if one of your web pages is currently ranked in Google at #3 for the phrase "wallpapers", it’s quite possible that the position may shift either ways after the new version of Google goes live.
Google has created a preview site (Caffeine) where you can play around with the upcoming changes before these get pushed to the main google.com website. And that is expected to happen in the next few weeks itself.
If you like to compare the existing Google ranks of your web pages with that of the future, check out Compare Google - this tools places the top 20 results from the old and new search engine side by side so you can easily figure out how your site will perform in the future.
Another Google comparison tool is located at Cartercole.com which, unlike Compare Google, displays Google search results in their original form - this is perfect for queries that trigger Google Universal Search so you can know what images and video clips results will get displayed in Google Caffeine for your queries.