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).
You say it will change or face disintegration, ( at least that's recognition on your part just how bad an organisation it is ) we cannot wait for that and take in 5 or maybe even 10,000,000 more immigrants. There are already millions who are in Europe from the middle east awaiting EU passports, the masses wanting to come to England will have already done so by the time anything happens and the Islamic state which will rise in a different form will actually be in England. We could not even deal with a few IRA terrorists in the 70's so lets not pretend we will be able to deal with thousands of Jihadis in 10 or 20 years who will be quite happy to walk into any apartment store, any cinema, any school with a suicide vest hidden in their vestments and destroy our lives. No not for me lets control immigration now.