This is no surprise to me. MAG were always going to court Ryanair and easyJet - it happens at every airport when it gets taken over. No doubt the new operators at Luton will offer incentives. The big winner is the customer.
Its what Luton has done so successfully since the new terminal was built, offering excellent packages to relocate airlines and/or routes from rival airports. Its the reason why the airport has grown by around 150% since the new millennium.
I have no doubt should the big 2 reduce their footprint at the airport, another carrier would step into the breach. I'm certain that Monarch and Thomson as well as other carriers that have no operations at the airport (Thomas Cook, Jet2, Flybe), have reduced or eliminated their services because of the threat of easyJet and Ryanair possibly blowing them out of the water. Monarch are already planning to operate an additional airframe from the airport next summer and with the fleet growing to around 44 by Summer 2014, I'd expect at least a 6th or maybe a 7th during the peak season plus more winter operations.
That said, I think the operators at Luton have been complacent for a situation like this for far too long.