Just yesterday I had a conversation with a person who studied economy and finances at a University. He said that any Economic system to work propoerly needs some inflation. Since Bitcoin is a deflationary currency by design he said there's no way Bitcoin would replace all the money in the world.
Not necessarily. You just need to keep the amount of money in circulation balanced with the size of the economy. Fiat (credit) money serves this purpose the best, but its power is often abused by governments...
You can believe me too, I also studied economics and finances, lol