LH can't operate B757's for one reason: this will cost them more. LH's fleet is made of an almost all airbus fleet. That's why they will be looking for an Airbus replacement for the A300/A310 fleet. I've heared that Airbus is developing an A330-100 that will look much similar to the A300 but with A330 wings. Airbus should rest assured by now, knowing that LH is a loyal customer: they have picked the A380 as well!
A300, A319, A320, A321, A332, A333, A343, A346, A388, B734, B738, B744, B772, B773, B788, F70, MD11, CRJ700