I assume easyJet are going to base an additional unit at Stansted to cover the Cagliari flight? My guess is - no!
The airline industry is in a cyclical decline, passenger figures are a statistic, the key is profit. if easyJet partially move out, it will only be a a result of slots at Gatwick becoming available.
If you think Luton is in mortal decline, you wait for the winter stats from the CAA covering all UK airports.
The art is to keep the profit, that is what easy and Abertis are doing?