Since they are going for larger planes rather than more flights that suggests they will be trying for more routes to the ME hubs. If so then that will mean more premium/business passengers for whom the airport currently have very poor facilities for
Stansted, like most non-prime airports, would really like a US route as well as further Middle East/ Asian expansion.
It's a very wealthy part of the country and it always surprises me than no airline makes a go of, say, Stansted to New York.
But the US seems difficult for airlines to make work from regional English airports.
Another middle eastern carrier seems basically inevitable at some point.
Qatar is flying to Doha from Heathrow about ten times per day. Ten! That's an awful lot of capacity. That's in addition to the two BA flights from Heathrow (which QR codeshare on) and the two Qatar fly from Gatwick. Eventually there will come a point they will see it's better for them to expand elsewhere around London.
Emirates flies to Dubai around (a mere) eight times per day from Heathrow, three from Gatwick and two Stansted. I wouldn't be surprised to see Stansted match Gatwick's schedule allowing Stansted to have flights for their three main hub banks.
The big Asian airlines seem happy to use Gatwick as their second option for the moment - but that might change.
But what is forgotten is that even with current airlines/ routes, expansion is needed.
Jet2 is moving from 737-800 (189 seats) to eventually be all A321NEOs (232 seats) airline. That's up 23%.
Ryanair is going from only 737-800 (189 seats)/ Max-8s (197 seats) to also having Max-10s (228 seats). That's a 21%/16% increase in seats - though they will be keeping the newer 800s and the Max-8s for a long time yet so obviously the Stansted fleet will be a mix.