If 8 billion people wanted to host their own email and web, yes, we'd not have enough addresses for each person to have one. That isn't the case though. It will never be the case. If we look into the future and say well in 2023 5% of the world's population ran their own email and web for personal or business purposes and that number were to grow by 5% every year then in 20 years we would run out. That's a worse case, contrived scenario but even in that case, we'd still have 20 years to come up with something better than IPv6 that truly respects privacy and doesn't track each person.