Yeah, once the series ended it's initial run, a bunch of fans (including myself) BEGGED for another a season... there was even a big petition started (back when online petitions SORT OF worked), and sent to both Cartoon Network AND John Dilworth; because of that, a fifth season was considered, but never saw the light of day.
HOWEVER, at the same time, a Courage movie was confirmed to be in the works (possibly theatrical as well)... but that never came to be either.