You CANNOT say a route is performing very strongly based on absolute volumes, load factor will be leading indicator and yield will be commercially sensitive data. Extrapolating high summer nos meaning YYZ could go year needs to factor in seasonality in Canada where the capacity is better used on Snowbird flights South to the sunspots of Florida and the Carribean. Canada-UK remains massively seasonal, and frankly so is USA-UK, nothing wrong or too alarming about a winter hiatus. MAN-YYZ remains seasonal whereas DUB-YYZ has both Aer Lingus and Air Canada, with AC serving YYZ/YUL/YVR and YYZ flown year round. The perils of the LHR option!
United only have 12 B787-8s and their range isn't needed on an EDI rotation but Air Canada only have 8 and they'll be back next summer!
The new A321s will be along soon enough and it's not as if there's not enough of them around already, you guys will miss the B757/B767 show when it's over.