We ask James Cameron to let the public decide. If they want a depiction of heterosexuality, they already got that with the theatrical version of Avatar. Why not a DVD version of Avatar where Jake gets to explore his sexuality instead? How about making the people of Pandora Transgender or bi-sexual? Or perhaps Jake should fall in love with a "male" Pandoran.
The point being, James Cameron has both the resources and opportunity to make this happen. There are no legitimate excuses for him not to.