I know maybe (and maybe not) other countries would leave if England does. Maybe the EU would become smaller. But will it survive at all, or will it cease to exist eventually? Although of course not right away.
In it's present form, no.
The UK is the only one of the "big five" likely to leave the EU. Spain and Italy are in no shape to get by on their own. France seems to think that it is the primary benefactor of the whole arrangement, and Germany actually is.
So at the moment everyone is waiting to see what it does. The EU has a history of attempting to bully small entities that won't dance to it's tune, so the UK would be a very useful ally in that regard.
If the UK left, there would most likely be some kind of domino effect that would see other countries leaving.
Most likely, those would initially consist of net contributing countries, since they would have much less reason to stay than those who are net recipients of EU handouts.
Also the EU presently has a huge public relations advantage, but that balance would shift dramatically once leaving countries started doing their own PR which didn't align with the goals of the EU.
So financial and public support would most likely be weakened, requiring some sort of policy change on the part of the EU. Given it's history and the history of monolithic bureaucracies in general, I wouldn't bet on any spectacular outcome in that regard.
Whether any such chain of events would eventually lead to a federal state consisting of the remaining countries or to practical disbandment is impossible to predict.
But what I am actually most concerned about personally, is what would happen to NATO if the EU was to act on any grudge it migt hold against leaving countries, rather than attempting to cooperate with them.
