It could happen one day, as long as Connor Benn continues to progress, it will be another 6-8 years maybe a decade away but if both are at world level there will be too much money in it for both of them to turn down.
Although he has fought at super middle, Eubank looks a natural middleweight so I cant see him going up in weight so far that he cant make weight at middle, C Benn is only 19 and he already looks too big to be fighting at super-light,, Id expect to see him at Welterweight naturally by the time he is 21.
Cotto, Khan, De la Hoya, Mosley all started at light/superlight, De la Hoya was even featherweight, and have all boxed at middle. As I said, it will all depend on Benn's progression but there is a fight there in the future if all goes to plan.