The best bet is for you to test them under 3.4 to be sure, and make sure all functionality is the same. It’s a good idea to start before it is released, and after the final version is out as well, to be sure that you caught everything.
Chances are, with the changes being made, nothing of normal functionality should change between releases. 3.3.1 isn’t too far off from 3.4, and the core is still relatively unchanged. The only way to know for certain is to test under a variety of circumstances in any case, whether the current version or not.
It’s always best to update your install when a new one is released for security purposes at least anyway.