Rumour I heard was that they have finally realised that the A319 is a bit too small, so they went to Airbus and said can they change some future orders to A321s. Airbus said "Oui, but get to the back of the queue and we shall see you in a couple of years" Hence sudden need for bigger shorthaul aircraft.
Suddenly realising that they already have the setup (pilots, engineering, etc) for 757s, in their infinite wisdom they are rumoured to be leasing some more 757s (models unknown).
Rumour supported by the fact that planned training and route cutbacks have not been implemented yet.