He WAS funny in GB II, but I don't think Dan and Harold would have any reason for him to return for GB III. Same thing for Dana and Oscar. I think their chapter in the Ghostbusters Story is complete. We wouldn't really need any of these 3 characters. If Peter was going to be in GB III, then Dana and possibly Oscar might be in it. After all, according to a 2 year old post I read last night, Louis Tully was answering some questions about GBI Franchises. He said that Peter lives in upstate New York now, with his Wife (Hmm, who do you think she is
). Peter is still the CEO of GBI. So I doubt we'd see Janosz, Dana or Oscar, if there was a GB III. But there's always room for a cameo…
Here's the link about GBI's CEO Dr. Peter Venkman that I found:
http://www.ghostbusters.net/disscussion/ghm/1/9958/