The Flybe online schedule suggests weekday Dusseldorf services are ending in late February and with a few cuts on other services (e.g. no Friday morning DUB, no Saturday DUB, no weekend Munich flights) then I guess this will make some space for replacement flying. With use of aircraft from other points (e.g. Manchester) then it may not need more based aircraft.
Those with longer memories will recall Flybe's last attempt at an off-peak Cardiff-Newcastle operation which didn't last long....