All,
It may be romantic to think that GR9 could be getting airborne again in USMC colors but it is worth considering the significant numbers of physical differences between a GR9 and AV8.
There is a logic to seeing what would be required - and it would be significant - to convert the UK to US version and see if that would cost less than the $30 million a copy to extend the life of the FA-18 a few years.
Doctrinally, if the conversion of GR9 to AV8 standard was cost effective it would blend nicely with the transition to F-35B.