Those "regulated Bitcoin exchanges" on Wall Street [ will ] be happy to take your real Bitcoins and give you dollars they borrowed into existence, and they'll be happy to give you paper Bitcoins for your Dollars, but when it comes time to actually redeem your paper Bitcoins for real ones it will turn out they won't have any.
I had understood that NASDAQ or other "Wall Street exchanges" would let people trade shares of bitcoin based investment funds like SMBIT and the Winklevoss ETF, not bitcoins directly. Or are there plans to have both?