Supposedly they are completely separate, so you should be able to uninstall 10. However, some folks have occasionally reported that the odd shared plugin disappears when uninstalling the old version. If that happens you can always reinstall 11 over top of itself to restore the plugin.

On the other hand, unless you're just plain out of drive space there's no need to uninstall 10. You might want to hang on to it at least until you're confident that 11 handles everything you want to do ok. Even after, you might find that 11 will occasionally not open up an old project properly so you may want to keep 10 installed as long as you still have some old projects to work on.