Huh? The PMDG 737 series are already “study level” (whatever that actually means).
If you mean by “default free plane with deep system simulation,” then a 777 would not be bad way to go but Asobo would be wasting money to do one from scratch, as PMDG’s own 777 is likely to come out this year, and they have confirmed that “friends of theirs” have already been talking with them about both 777X and 787 models.
That said, the 777X is not going to enter commercial service for at least 2 more years so what’s the rush?