Which number seems implausible to you? The current world's population? The number of bitcoins that will exist? 2.1E10 divided by 7E9? Cause they're pretty much facts, aren't they, unless I made an arithmetic error?
Sometimes I think the color of the sky seems implausible, especially at sunset, nevertheless it is what it is. It hardly seems worth arguing that established facts seem implausible.
Bitcoin's eventual mass adoption is implausible to me.
If bitcoin doesnt appeal to the mainstream, then none will. Bitcoin is the friendliest decentralised currency to regulation. If you are asking for a centralised crypto like googlecoin. go for it. but that will be unacceptably vulnerable to attack, and prone to corruption like our current banking system.
Bitcoin can appeal to the mainstream, just leave that up to the software developers.
Governments will never give up their monopoly on money, and with the government bans, Bitcoin won't appeal to the masses. The masses find their comfort in governments and always turn to them for guidance, advice, and comfort.