I have fond memories of both that and the first game. But I'm kind of worried that they've aged really badly now. Especially the early 3D era sequel. I might be wrong though.
The rights are with Squee, I believe. Who aren't on GOG and have about 100 games they're going to be more interested in releasing on GOG first if/when they do show up. Which is a shame, but there you go.
I don´t think that the first Carmageddon aged bad, the second one maybe. I´ve played it recently using DosBox and it was really fun, and it worked fine without any bug (GOG this is for you :-) )
I think that EIDOS owns Carmageddon´s rights.