Monster Hunter XX (double cross) is the update to Monster Hunter X (cross) which was Generations in the west.

While XX will have additional Monsters areas and updates to even out the play styles and skills it will still be the same play style as Generations. There has yet (as I know of) Been any conformation of "G" rank in double cross, just more quests and more difficulty quests at higher levels.

Also so confirmation of a western release but since the Switch is region free you can still import or download it. E3 is next week however and we may hear something then as well as more answers to your questions.