You can't take anything said on an AMA as official until it's written in a post. We've seen details change many times over the years for lots of issues.

If you think that there will be enough packs to go around, then you don't need to buy XCHAOS unless you want pro-rated airdrop value. This can be an advantage if you don't plan on buying hundreds of packs.

Personally, I don't think there will be enough to go around.