A number of reforms that benefit Britain will be activated almost immediately or within the months after a "Remain" vote, so the status quo will already have shifted in the UK's favour compared to the situation right now.
http://www.theguardian.com/politics...special-status-deal-if-uk-votes-to-stay-in-eu
And with the drumbeat for referenda growing louder in France, the Netherlands and other countries, the EU is going to have to seek to change to quell similar "exit" calls as the one which would have just been defeated in the UK.
It may not change as much or as fast as many people would like - in fact, it's almost guaranteed not to given the need to form 28-country consensuses. But it will change, or face disintegration at some later date from some other vote (and in the latter case the "Leave" camp win what they were after anyway).