It's not clear if this will be enabled by default, or how Google might prevent accidental Assistant use outside of requiring specific timing (will it inadvertently react to an ongoing conversation, for example?). The apparent leak also doesn't indicate whether or not raise to talk would be available on launch. Other rumored Assistant features, like the ability to take over calls while you're on hold, are believed to be too rough around the edges to be ready for launch. If this is accurate, however, Google will lean heavily on Assistant upgrades to sell the Pixel 4 in addition to its hardware tricks.