The reason for this delay is wanting to get the Linux 4.10 kernel into Debian Stretch. Linux 4.10 is desired since it is expected to be an LTS kernel that will be maintained longer by upstream and offer improved compatibility.
The revised plan is for pushing all milestones back by two months, which means the transitions freeze is now 5 November, the "soft" freeze is 5 January 2017, and the full freeze for this next major release of Debian will be 5 February of next year.
Today's delay message makes it clear they will only cater towards the Linux kernel and aren't looking at shifting the Debian release time-frame for other software components. "For the avoidance of doubt, this change is a one-off to align with an expected release of Linux only. We aren't in a position to try and accomodate other projects, however much we'd like to be able."