The computers will stop generating bitcoins at 21 million because that is the way bitcoin mining is programmed. Every couple of years the amount of new bitcoins created is cut in half, so the supply of new ones is exponentially decreasing.
Very few people will ever own a full bitcoin. Unlike the dollar which is divided into 100 cents, bitcoin is divided into 100,000,000 satoshis. So even a a $1 million bitcoin, that’s still only one cent each.
And nobody can change the programming? You have seen the source code?