I don't think the Hellcannon is all that scary... faced it only once or twice, but it didn't do a whole lot of damage.
I have read in a couple of places, a few coments that seemed to let on that GW plans to do both a DOW book and a CD book... take that for what it is though, just a few comments read on the internet... but anyway, I would think the Hellcannon would be in the CD book if it were going to come out again in a book... so this is just me talking out of my hat here, but if it isn't in the Chaos book, maybe look at that as a good sign for the CD.