I wonder what would happen to UKIP if "Leave" win?
If we leave:
They will spend the next 2 years making sure that the split is negotiated in the best interests of the UK. For example, if the EU offer is access to market in exchange for continued free movement, they would resist this as much as possible. There are also numerous other things that have be split (fisheries, agriculture, trade, energy) that will require negotiation.
Then there are other trade deals to consider, and where should you start? According to UKIP, start with the commonwealth first, then rest of the world. Reason being, we can't at the moment, as we have to follow the EU tariffs on trade.
There would then be continual campaigning to ensure that the UK remains independent.
Think of it like this, if the SNP gets independence for Scotland, will it fold over night? No, of course it wouldn't. UKIP is in the same situation.
If we stay:
If it was a close call, expect it to be contested, and talked about for ages, and in 4 years time expect another referendum (with a different Prime Minister and probably leader of the opposition to, depending on how he handles Chilcot could be sooner than later). Expect UKIP to keep going.
If it is a slam dunk stay, then UKIP funds will probably start to dry up, as supporters have been and tried, and failed.
Either way, don't expect to see Nigel Farrage leaving your TV screens anytime soon.