I don't know about a billion dollars, but I do know that Japanese JW's and some others will help out the handful of JW's actually affected by the disaster and WTS will take in millions toward the worldwide work while spending a handful of that money on those few people.
There will be stories of how the WTS was best organized compared to anyone and how they even helped non-JW's. There will be stories of how their incredible love for the brotherhood caused some people to start studies.
But mostly, WTS will ask for more money to help, but please don't earmark the money for the disaster. Just send it and "We" will know what is needed and how best to use the money.
I actually picture WTS honchos licking their lips when such a disaster as an earthquake where very few JW's live happens. It works so well with their belief that the end is near and it helps pay for the cult publishing corporation.