No, iOS users can already use Chrome, they just can't use Blink. The difference is whether Google can leverage their developer base to drive people to Chrome without having to provide a superior product to the consumer. Today developers have to support WebKit to get iOS users, instead of just throwing Safari users a popup that says "fuck you, download Chrome" like they do on desktop. I think it's at least arguable that many would prefer to do that than continue to support WebKit.