Theoretically, it surely can, but I don't think that rich people will do forex as their full time job. It also matters, which rich people we are talking about. I mean there are some rich people who earned the wealth by themselves or there are also rich people who became rich by chance. So, I believe that those rich who made their fortune on their own will never turn into poor because of forex because they know the principles of economy and markets and money management, so they are highly unlikely to lose the fortunes trading currencies. However, those people who cannot manage their money can lose their fortune quite easily.