EZY have had a good year however what exactly 'good' means will only be known by those at the top.
It is now over five years since NCL went down to three aircraft. If it is doing well now with the current set up then a fourth aircraft might hit the economics of the base so I cannot see it growing any further. If it did then a summer only fourth aircraft would be the most likely but that would be a good few years away.
If U2 made a proper effort with easyJet Holidays there's no reason why they couldn't have the success that Jet2 Holidays have had. But as it stands it seems more of an after thought and very little different to simply buying a hotel during the flight booking process.