I wouldn't be too concerned about EZY. They are in their sixth year of operation, if SEN was a lossmaker they'd have left by now. I still have doubts about the longevity of CDG but other than that everything seems to tick over nicely, there continue to be new routes added and I often find fares on Med routes to be significantly more expensive than other airports.
If any downturn resulted in consolidation I'd suggest it would be STN most at risk, and SEN could be a beneficiary of such a scenario. They could easily run routes such as Asturias from LTN, and send a couple of aircraft to SEN to bump up frequency to the likes of Ibiza and transfer over sunshine routes like Dubrovnik and Split.