Definently buy the game. Although it is different that Jeff's other games, so I advise trying the demo first, if you haven't already. It is a very good game.
hmm.. a sci-fi might be interesting. Having lazer guns and blasters... running around on alien planets... I can almost see it happening.
But the Aztec thing could be pretty good also.
A Nethergate 2 would be fun. I really liked the mood of the original, but I didn't think that it left much room for a sequel of any sort. A prequel maybe.