Well in all fairness BRS has been without an IOM a service for quite some time yet that route is being revived, this time with an Airbus so anything is possible. Nothing surprises me these days.
I heard a rumour the Manx govt. pays some subsidy for new route. Not sure if there's any truth in it (im sure some make stuff up just for the craic!) but with NCL being a current route perhaps there's less chance of it switching to another carrier as there's no incentives for them and they would have them taking on the full commerical risk.
Potentially however it could work. It's accross the sea. There's no cheap or quick alternative so you should manage a decent yeild together with the lower operating costs of a short hop it could be a winner.
I however know zilch about the demand on the route nor the demographics IOM so who knows!