I don't think Boris would take the risk of a second referendum, as he, and the Tory party have constantly said they will respect the first referendum.
Labour did the same, they promised to respect it, then over time they've basically said screw the result, we think you got it wrong, we want to stay.
Plus, if Boris wanted a second referendum, why do you think he's been pushing so hard for an Election?? He wants an election because he knows at this moment in time, there is a very high chance that the Tory party would cruise to a majority, meaning his deal, this one, or any other, would be easy to get through. In the same sense, thats why Labour want a second referendum. They know their chances at an election are slim, so they want to try and stop brexit regardless. Corbyn on the other hand is extremely confident and wants to go for that majority.
So, as it stands, there won't be a second referendum before a general election. I'm pretty certain of that. Now who wins that GE could change everything.
Just think of this too... Both Labour and Conservatives support a second referendum, Leave voters of both parties feel betrayed, who do they go for? Only one party willing to get into power and pretty much pull us out of the EU no deal. Thats a pretty scary prospect, and with how volatile things are at the moment, it's safe to say anything is possible