The Patch 10.2.7 PTR splash screen indicate that Timerunning: Mists of Pandaria will release 1 week after the launch of Patch 10.2.7!
We've datamined the Patch 10.2.7 splash screen:
This indicates that Timerunning: Mists of Pandaria will go live 1 week after Patch 10.2.7 launches, leaving players with a week to complete the 10.2.7 questline, collect their Heritage armor, or more!