Range would be equal to todays B777-300ER. Pax config depends on the stretch for sure, but assuming around 5-6m in length could result in around 40 add pax in a 3-class layout.
This program was studied by Boeing, but stopped due to the B748I-Development.That was the reason for my big IF
in my post...
But time will tell, if the airlines could be interested in it again.The B777-family will have to find its place in the new Boeing-Range with big B787-versions, so a further stretch could be an option together with improved and increased wings and engines.The possible launch of such a family -400X, 300F and 300LR is strongly related to the success of the B748-pax version.