Project P-42.
From Savannahnow:
"Whatever the project code-named P42 looks like, most industry insiders agree it will be Gulfstream’s answer to the Falcon 5X, which has a wider cabin and the ability to fly 1,000 nautical miles farther than the G450.
Aviation News has reported that the P42 is a clean-sheet successor to the G450 and will build on the all-new wing, fuselage and systems of the G650.
Perhaps the most intriguing aspect of the P42 is the report from Aviation News that General Electric and Pratt and Whitney appear to be the front-runners to power the new aircraft after Gulfstream ousted longtime supplier Rolls-Royce from the contest.
If confirmed, the decision would mark the first time in more than 50 years a heritage Gulfstream business aircraft has moved into final design with a non-Rolls engine."