While most routes are pretty much already covered with alternate flights, and better run airlines are already looking to move into markets where there's an actual demand or PSO (like Newquay-London), expect wailing and gnashing of teeth from people relying on ridiculously cheap tickets.
Most routes are not covered at all. At least 3 airports I can think of have lost the vast majority of their flights. While the users of the flights from Exeter and Southampton on the most part may have a practical alternative I doubt those from Belfast are booking rail travel any time soon.
Flybe made a massive misstep when they took on stupidly expensive small jets and tried to take on the big airlines with longer flights, their bread and butter domestic and regional flights were by all accounts doing ok.