It seems from Dec. 4th they are going to alternate the AF406/401's 777 (the "regular/old" one, the new one being coded 403/302, always BEST, 787) with NEV4 & Best. So one would have to be extra-careful when booking from this date to make sure they're served with the BEST 777, and not the NEV4.
I'm assuming they will deploy BEST to SCL on all flights at some point, but not in December at least.