Often, to predict an outcome in these things you don't just look at the polling question on the issue but attitudes polling/surveys to gauge a picture. That's why even when 'Out' was behind by quite a margin in direct EU polling one or two years ago I wasn't consigned to defeat because I knew the background polling/attitudes of the public were instinctively deeply eurosceptic. From that, I knew it was possible to win over 50% of the public to back Leave - it was simply a matter of running a convincing campaign.
One of the striking things about France and this election was a survey that came out a while back which suggested French voters are most longing for a 'strong leader' ..... so you can guess who this fertile discontent will benefit most.
I'd say all bets are off. It's possible.