Got to agree with HMB again - LS and TOM are very quiet during the winter, so to say they are 2 strongest is nonsense (in fact, is TCX not on a par with TOM?).
I've noticed no loyalty in terms of airlines - people pick and chose depending on what suits, and when booking themselves it's not unknown to be going out on one and back on another.
Getting back to the original point, the concern is not about sustainable expansion but about whether non-based additional capacity is going to lead to a reduction from the based operators, which would have an impact which would outweigh any benefits