Maybe someone has already experimented this situation:
You’re hacking on your local working copy and you want to keep it up-to-date but, since you have some uncommitted changes, git-svn rebase cannot be executed
I was just thinking to write something about this problem when I read a post on digikam blog.
In this post Marcel proposes a workaround using a bash function. In fact there’s a “cleaner” solution, if you’re interested read the last part of my git-svn howto.