ARK Invest CEO Cathie Wood says the US dollar is much stronger than investors think and could appreciate significantly over the next few years. Wood says the dollar has gained 36% since August 2008 on the Federal Reserve's broader currency index. A stronger dollar could pressure gold, reshape bond positioning and test Bitcoin's recent gains. Morgan Stanley's Amy Gower still sees $4,000 as strong support for gold, helped by central-bank buying. Bitcoin gained 6.14% in September while the US Dollar Index also rose, potentially signaling a weakening of Bitcoin's usual inverse relationship with the dollar.