According to https://swift.org/blog/swift-4-1-release-process/
Four notable exceptions to this plan are swift-package-manager, swift-llbuild, swift-corelibs-foundation, and swift-corelibs-libdispatch which will merge from master into swift-4.1-branch daily and whose final cutoff date for changes will extend beyond December 4 and will be announced later.
I wonder if the date is known already?
This should have been communicated but wasn't. Swift 4.1 is in the final stages of convergence, so it certainly isn't taking changes from master at this point for all repositories. Active development at this point is focused on 4.2.
I apologize for the poor communication here. It slipped my mind (and others) to communicate the cut-off for these repositories. With different owners of these sub-projects, there was a bit of a bystander effect here we need to recognize and remedy for future releases.