This is a heads up that we're planning on feature freeze for Julia 0.6 by the end of 2016. Shortly following that, we'll put out 0.6-alpha, which should have all the major features of the release. By end of January, we'll put out 0.6-beta, which will be feature-complete but still include some known release-blocking bugs. Once all known release-blockers are fixed, we'll start the RC process.
This means that any new or changed feature that are going to be in 0.6 must be completed by end of year, so any new features should only go into the milestone if someone is committed to implementing them by then. The release of 0.6-alpha is also a great time for people to test the new release and start updating packages to work with 0.6.