The really crazy thing to imagine is what will happen if the owners of some VERY old wallets with a lot of BTC in them come forward and offer to be the funders of future tools based on BTC. There are a few wallets that could potentially grasp control from larger institutions if Bitcoin was moved to a more prominent position in the financial landscape.
I'm not really much of a conspiracy theorist but imagine something like that has been the long vision this whole time!
Well keep in mind the Wall Street firms will use USD as the unit of account. So the number of BTC needed declines as the value goes up.
It actually works out well for them to ride the wave up and then collateralize it.