Warren Buffett has made billions thanks to his ability to bet successfully on investments over the years. Now, it looks like he's about to win $2 million more.

In 2007, Buffett made a bet that the S&P 500 stock index would outperform hedge funds, which he describes in a 2016 letter to Berkshire Hathaway shareholders. He argues that over a period of time, active investment management by professionals would underperform the returns by amateurs who were passively investing.

Buffett publicly wagered $500,000 and suggested a 10-year bet. "I then sat back and waited expectantly for a parade of fund managers ... to come forth and defend their occupation," Buffett writes in the letter. "After all, these managers urged others to bet billions on their abilities. Why should they fear putting a little of their own money on the line?"

Only one person, however, took the bet, according to the 2016 letter: Ted Seides, a former co-manager of Protégé Partners, a specialized asset management and advisory firm. In a Bloomberg post, Seides says that the two agreed to the wager, which pitted low-cost S&P 500 index fund returns against a group of Protégé's handpicked hedge funds.