Well...ok, you have one assumption correct.  If 'the world itself adopt Bitcoin' then yes, it will obviously 'be huge'........I mean, I'm just guessing here - but I don't think it'd be small....

But central banks...adopting a decentralized currency...dude...what

BUT if perhaps by 'adopt' you meant "find ways to easier steal their users' money through blockchain technology" then yes, I'm with you there