First off, yeah, canon is your call, so if you like the idea use it.
That being said, I've always leaned toward few if any Dilgar. I can't imagine that the League would have left any colony standing, but a few tough veterans might have been clever enough to hide for a while. As an organized group, my vote is no, no Dilgar left. As individuals, I think there have to be a few out there that have managed to hide. Deathwalker hid with the Minbari. Perhaps others went far enough away, or paid off some people to hide them or even took shelter with the Drakh. It's a big universe and it's hard for me to imagine that every single member of a species got wiped out.