Hi, somewhat new to the board (was active on a previous iteration) but may be familiar to some from other boards. I am somewhat Shik's assistant in this project.
To answer about the Enterprise-G: the project as it stands covers registries up to NCC-100000, as mentioned above, which takes us roughly to the year 2400. In our timeline, the Enterprise-E is still in service by 2400. Which, when you consider STO has the Enterprise-F coming online in 2409, is not too far fetched.