Both, ish. We definitely want to replace bits of Gecko with Servo code (in general, Rust code). That is already happening. Servo development is still continui

Both, ish. We definitely want to replace bits of Gecko with Servo code (in general, Rust code). That is already happening. Servo development is still continuing. Servo and browser.html are evolving in the direction of eventually becoming a product. We don't know right now if they will. In the meantime, Gecko can reap the benefits.