With respect, I disagree. Rendering pages quickly and reliably is table stakes and all modern browsers do a great job of that. It doesn't really matter at all what rendering engine is under the hood as long as it works well.
I'm glad we have three rendering engines, especially since the largest two are backed by companies who don't always do what's right for the web... but three is enough. More than that would honestly be a waste of effort, I prefer the current situation with hundreds of browsers who pool resources and work together on a rendering engine that is shared by other browsers.
What really separates one browser from another is the toolbars and other user interface elements around the webpage. And Blink/WebKit/Gecko don't provide any of that.