yup, you're right! 6.4bil. i thought i had gone all the way back when there wasn't any "prev set" but guess not. it happened in 2010 and he had 90mil acres!
I think 7b is still possible. Look at SV's countries from a few sets ago when he put up sixteen 470m countries. Sure you will loose some of the NW when attempting to transfer, but I think he even mentioned he could have put up even more networth that set.