Im worried about bitcoin because wall street can be manipulate Bitcoin in the next years. Creating chaos by selling non-existent bitcoins only in the form of a contract. This is against the very nature of bitcoin and can turn everything upside down. Although it seems to be positive in the short term.
PayPal is doing it already. Selling bitcoins and won't be able to send outside their platform. Your worry is legit IMO. But as year passes by, investors are becoming more intelligent.
They get to understand what would be on those indices and the actual bitcoin that they can hold, send and receive.