I think its just count until you hit three digit. So F95 in the next gen would be a G. Since F95, G05 are just model numbers if you look in the past they just keep adding up and start at E go to F and now we are seeing G start....
I could be overly simplifying it but that is what it looks like to me.
Some links:
https://bmwcarclubgb.uk/e__f_numbers...%20F%20numbers.
https://en.wikipedia.org/wiki/List_of_BMW_vehicles