Bitcoin has definitely a good future ahead of itself, but that doesn't mean you'll become a multi millionaire. For that to happen you'll need at least 100 BTC if you calculate that the price at some point will reach the $10,000 level. Keep in mind that the majority of the people holding Bitcoin hold an amount lower than 1 BTC. How do you expect people to become millionaires with such a low amount?
Nothing can be termed as impossible. Even those holding 1 BTC will become millionaires, if the exchange rate increases to $1 million. I know that it sounds ridiculous now, but anything can happen in the future. In 2012, no one thought that the exchange rates will go up by 100X in 2013.