Should they want to grow and stay sustainable they need to get out of Ireland. I'd say they'll set up a couple in Britain
HOWEVER, and this is why people think I'm negative (!).....
The cost of setting up Belfast was quite high, base expected to lose money for a period in a new market. Couple that to the riskier move into the Orange Fortress at Gatwick and the already busy London market, profits from here are some way off. Add the current cut throat climate to that, and then suggest adding a new base somewhere in Scotland not threatening an existing Ryanair base.
Perceived wisdom, which is frequently utter rubbish in real life anyway, says that ALL airlines need to grow to survive. This is true of Ryanair and their business model coupled to massive expansion tied into aircraft orders and trading. I can think of a lot of airlines that have been here for years, continue to flourish and look like good bets to survive the current storm AND are not involved in a massive growth frenzy.
There is WAY too much air travel anyway. We don't need all the airports we have and proper investment in a core set of airports would be better for everyone. However we want airfares that cost less than the taxi home so don't expect anyone to listen to my "John the Baptist" moment here. Are Lingus are not involved in sustainable growth, Gatwick is an opportunistic bet that may or may not work. Belfast was always on the cards, outside of that, the UK is already OVERSERVED with airlines and choice.
Globespan survived ( and are prospering )in Scotland once they got out of the over served STN / LPL bases and the insane dash for long haul. Aer Lingus couldn't do the same in Ireland?
We are being presented with a fait accompli that says that Aer Lingus CANNOT survive on Ireland alone without adequately explaining as to why not. There are some good examples of airlines that do serve their home markets exceptionally well and live on, the temptation here is to imagine a load of green tails on the South Terminal at LGW with A330s serving London- New York ( the most competitive route imaginable at the best of times ) is the answer. People, I think you got the question wrong before you arrived at this answer.