While it’s certainly not impossible, I would be pretty shocked if Apple dropped WebKit in favor of Blink. The entire reason Blink was forked in the first place was Apple and Google’s differing ideas on which direction to take the project.

Where Google favors getting new features in at a breakneck pace and sees the browser as an OS-like platform where the developer rules supreme, Apple favors power efficiency and sees the browser as a content portal where developers can’t be trusted to work in favor of users. These two models are fundamentally incompatible.