Borderlands 2 is probably going to happen, if comments made in this interview are to be believed. Mike Neumann told the award-looting VG247.com that “Everyone here loves the franchise, and it seems like the public is really coming back with praise and love. So yeah, if everything makes sense, Borderlands 2 seems like a no-brainer to me.”
The downloadable content, Zombie Island of Dr. Ned, will reportedly cost $10 and is out on the 24th of November (not clear if that's for the PC). Still no patch addressing voice and connection issues though, eh? Or did I miss that? Anyway, what do you want to see in a sequel?