surprisingly, a huge chunk of the animal kingdom are hermaphrodites. The gender only comes into play when they want to reproduce. A few examples are Snails and Fish
Anyway, Do you think we will see hermaphrodite pokemon? I'm not sure how they will work, maybe their gender will change weekly or something. I doubt this would do anything stat wise, but I think it would be interesting at the very least.
I hate people in general. http://w11.zetaboards.com/NPC/index/
Ditto is a perfect example of this, and the only one even necessary. There's absolutely no reason to introduce more. It would serve no purpose at all, unless ditto goes extinct, and they want to introduce a new "breed all."