The looser in the long run for this is likely to be Aer Arran, if the airport can find another carrier to pick up these very successful routes and maintain similar prices.
Aer Arran will end up flying to an airport where no one wants to go to and will be unable to come back LTN if someone else comes in and picks up where they left off.
I hope the likes of FlyBE are willing to pick up the routes, but not too sure if it will be them... They seem reluctant to fly other routes out of LTN with their main base for London being south of the river.
The only reason the the IOM and JER routes work is because they are operated from these respected bases. It would work if the airline offered some sort of W route, like:
IOM-LTN-WAT-LTN-GWY-LTN-IOM
or
IOM-LTN-WAT-GWY-LTN