Well, people who bought bitcoins back in 2010 & 2011 by investing a few hundred dollars are already millionaires.
There are speculations that 1 BTC might go as far as $500,000 in the future, but nobody knows if this is possible. As nobody knew bitcoin would go to $2000 USD.
Only time will tell how the value of bitcoin will change.
But, no matter what, the sooner you get into this revolution, there are high chances you might end up becoming a millionaire in the future.
Most of us are safe investors and bitcoin is a highly volatile currency.