I think another good use for this might be that if you want to start a new file after you beat X/Y but don't want to lose your pokemon you can save them all on the cloud.
I've wanted to play some of my old pokemon games again but deleting the hours of stuff I did in them is too painful.
I don't think an XL version could happen since the controls are already moved up on the normal 2DS so that you can reach the triggers at the top, on an XL version there would be too much weight unbalance with your hands at the top of the bigger screens especially for smaller hands.
SorrowSurvivor's comments