I hope that you're wrong! Google already has a tremendous amount of influence, and a Blink monoculture would give them near complete control of the future of the web. (And I think Google have been poor stewards of the web. But that's an entirely different conversation.)
Blink being open source is better than the alternative. Internet Explorer achieving total dominance would have been even worse. But it doesn't buy you that much. Under a monoculture, your fork of Blink could never deviate from the original meaningfully because sites wouldn't be built to standards, they would be built to work on Blink.
Google not being able to unilaterally dictate web standards is a good thing. For example, I'm glad we have WASM and not Google Native Client.
It's the web's destiny anyway. Its design lacks modularity to such a huge degree that a monopoly open source implementation is inevitable. There's no deep reason that has to be bad, Blink is open source and can be forked. In some ways it's not really clear what benefit the duplication between WebKit, Blink and Gecko brings to the table nowadays, as they implement the same specs in essentially the same way.