I can't see Flybe stopping the INV routes to be honest, I travel on the current BAcon service at least once a month - often on the middle of the day sector and even that is fairly full. And if its a Q400 instead of a 146 the load factor will be higher.
I'd imagine that Flybe would make a packet on this route with their baggage charges and i'd be surprised if the INV sectors don't sell more food & drink than any other, on my trip last week I sat in the middle of the plane and it took the FA's nearly 30 mins to get to me and they weren't dawdling