http://blogs.wsj.com/moneybeat/2016/06/20/who-to-trust-on-brexit-predictions-the-pollsters-or-the-bettors/
OPINION POLLS IN THE RECENT PAST:
Pre election opinion poll forecasted a marginal victory for David Cameron, but he won comfortably.
Lean victory to say 'No' in the Scottish referendum ended up in a decisive win.
CONCLUSION:
Going by the above, my forecast would be that Britain will remain with a fair majority voting in favor.