It's unlikely that San Francisco could ever supplant
Wall St, despite San Francisco having a large financial centre.
Is this actually that unlikely?
Look at the tremendous wealth creation around the Bay Area over the last three decades. There's an unprecedented flood of capital to the area, including private individuals and international investment firms. If you look at the actual numbers, it's astounding and can't really be described as a "bubble."
In the 80s, companies would hold a public offering when the had <$25MM in revenue. Today, companies try to stay private for as long as they possibly can, which has resulted in massive private financings. See Square, Uber, Dropbox, Airbnb, Twitter, etc. These are nearly always being led by investment banks, like Goldman Sachs.
It's not outlandish to imagine a secondary financial market emerging in SF, designed specifically to fuel the sort of innovation the region has become famous for. The huge banks in America (JP Morgan, etc.) were essentially a result of the industrial revolution. If we're in the midst of another revolution, it's likely a new banking group will emerge.
The way of Silicon Valley is to innovate solutions. Nobody is going to try to appeal Sarbanes–Oxley. We'll just build a way around it. Even with it's warts, Bitcoin is one example. Full democratization of commerce and investment is inevitable.