I can not imagine replacing a 5 year old G650 for what another G650?
If the G6 was out then I could understand that change perhaps with the logic the G650 has some challenges at certain airports due too weight and wing but not age.
Plus, they already show they are ok with keeping a 10yr old jet...
Some clients may have issues with a aircraft that old and they are updating because of that. But Las Vegas Sands flys GIVSP's still and even older 747Sp and L1011. So age may not be that big of a concern to passengers.