Why wait for a new project? Git and Mercurial both support some bidirectional SVN integration. This means that you can pull changes from the SVN repo, and do your own DCVS thing, then push your commits back to SVN. Your project partner can keep using the SVN repository, and generally doesn't even know that you're trying something new on your end.
Assuming that you're using the conventional SVN project structure, all you need to do is a quick git svn clone --stdlayout file:///path/to/your/repository and you'll be up and running. You can make your changes, commiting to your local git repository, then just git svn dcommit to push your changes back up to SVN. If it bothers you about uncommitted changes just wrap it up in a git stash; git svn dcommit; git stash pop to store your working copy (eg, your project file, temp files, partially edited config file containing passwords and whatnot) commit and then restore all your extra files. To pull changes from SVN, you just need to git svn rebase to apply your changes to the current head.
Do note that branches and tags aren't propagated back up to SVN if they're created in Git, but that's not such a big deal. You can still merge stuff down into master and push it up to the SVN repo. (There might be a way to get it to work with branches, but I haven't looked at it)
Go give it a try on a private repository. There's plenty of documentation out there (for once), so it's easy to get started. Just beware -- you might like the new workflow.