I think that I read somewhere that this takes place in a time frame that allows a ship to to get to Pandora from Earth, plus a few years AFTER the ship carrying the kicked out RDA shows up on Earth. We ALREADY HAVE the technology to go to the bottom of the Marianas Trench, and have DONE IT, they are 150 years in the future, have cryo, and near light speed technology, so being able to put several deep divers on the far side of Pandora would not be a big deal. Why? perhaps because they want to build an under water base there, though they would not need to go very deep at all to not be bothered by the Na'vi.
Wouldn't it be interseting if a parallel developing species of sentient life were on the moon that had been warned by Eywa about the humans, or BETTER YET the beings in "The Abyss" WERE "Eywa"???