Since I won't read onward I think it's okay for me to say what I initially thought and how I changed my opinion.
At first, I thought Zoro and Sanji will get King and Queen's bounties on top of their own ones. Then I thought Zoro will have 1.4 and Sanji 1.3.
Now I think that it will be good if Zoro exceeds the 1b bounty mark.
Ain't no fucking way Zoro will have half of Luffy's bounty at this point in the story. We are in the big bounties league, Zoro won't have incredible bounty jumps from this point onwards.
So anything like 1.5b for Zoro is completely impossible since it would be half of his Captian who happens to be a Yonko now bounty.