Official answer = I don't know. A best guess? Have to look at this in a few ways. Large corporate banks like BNY, JPM and the like are already embracing crowdfunding and other related Fintech startups in many ways. One way is to sponsor young entities. I attended an event hosted by Barclays accelerator - where Barclays helps nurture startups with office space and mentoring. In a perfect world - banks that sponsor young companies that have a chance to grow into micro caps, and rise up to be the next Unicorn and IPO and go forward. Think of it like the "NBA Development League" of of prospective growing companies who could - as they grow - have an ongoing relationship with the large bank and with each succeeding year potentially consume more and more banking services.
With regard to Equity Crowdfunding - I would think the large banks would continue to push issuers to pursue an IPO than say a JOBS Act / Reg A transaction. I see the large banks being a "me too" entrant into the equity crowdfunding space. Can they make enough money working on a small capital raise - unless there is a large ongoing dealflow? Hard to say. There are many niche players who are working in the Equity Crowdfunding space, as well as equity crowdfunding portals, some of whom have broker dealer arrangements. If there becomes a steady stream of "sexy" Reg A and A+ transactions - and more having a high visibility in the market - I could see large cap banks perhaps making an acquisition to enter the space.
Just my $0.02 - and a guess.