One word Cibaman - STEALTH!
How on earth did we get from a common market where everyone could sell goods to each other to where we are today?
Can we join the Euro by stealth? Will Turkey join the EU by stealth?
Clearly there can and will be gradual steps towards further integration by stealth. But that final stage of full political integration cannot be achieved by stealth. If the vote is a narrow win for Remain I would expect that any major treaty change would need a referendum.
It was said before the Scottish Referendum that it would be the only chance for a generation for the Scots to vote for independence. But does anyone really believe that now? A recovery in the oil price and some major event impacting on the relationship between Scotland and the rest of the UK would result in a second referendum.