If the referendum result is to remain, what stops the EU from continuing on as 'they' (whoever 'they' are) wish re. transparency and accountability? Once we decide to stay, they can say "well, this is how it is, you're not leaving, so that's the end of that."
Perhaps that will become the main argument for leaving -- that if we don't, then we end up on the irreversible path to 'ever closer union' and the referendum might be the only chance to stop that (if indeed we want to stop it.)
Would being part of a federal Europe be a bad thing? The case of Greece makes it seem that more flexibility might be better for individual countries than being too tied together. But I'm not really sure either way.