For AS9100 Rev D the date to transition from an AS9100 Rev C certified QMS to the new standard has always been aligned with the ISO 9001:2015 transition dates. In September 2017 the ISO & IAF group put out a news release stating that this date for transition would be September 15, 2018. After this date no certification for ISO 9001:2008 would be valid, and likewise certifications for AS9100 Rev C would not be in effect any longer.
Of course, there is no last date to certify a new QMS to AS9100 Rev D. This will be the aerospace standard going forward.
For more information on AS9100 Rev D transition see this whitepaper https://info.advisera.com/9100academy/free-download/as9100-twelve-step-transition-process-from-rev-c-to-rev-d