Dooooo iiiitttt. You know you want iiiiiiitttttt.
Seriously, not sure about whether Apple would add GPS next gen, but I sure want it. And I would love for the watch to get thinner, because I'm a small woman, and even the 38 is a bit big for me. FaceTime camera is about the only thing I'm not interested in, because trying to hold my arm at an ange where the camera is not showing my nose hair would get tiring very quickly. All other things would be incremental upgrades, but taken together would be a nice upgrade package. Then Apple always manages to throw in one more thing that I haven't thought of but when I hear it, I want it. I keep on telling myself that this year I wouldn't upgrade my iPhone and iPad, then end up doing it every year. I expect the watch to be no different.
That said, if you get the watch now, you'll get a solid year's worth of enjoyment out of it. So if you like playing with new gadgets, and the price of the watch isn't going to eat a hole in your budget, by all means, you should go for it.