What I understand this referendum is not legally binding. So even if the 'quit' camp wins, this will finally boil down to parliamentary politics in UK and it will involve prolong negotiations, both within the country as well as within EU and might take anything from 2-3 years. So a 'quit' doesn't necessarily mean 'quit' in actual terms.
Market though is a different beast. So it would react in its own way.
By the way, a Britain out of EU would actually be better for Indian trade and commerce. But chances of 'remain' camp winning looks better as of now.