Dark Knight III: The Master Race #6 has been removed from the publisher's schedule with plans to resolicit "at a later date", according to a retailer mailing sent out Wednesday by DC. Originally solicited for June 15, DC's website hasn't updated and still lists #6 as "on sale now," and the collector's edition is currently listed for September 14. Previous collected editions were released two weeks after the first edition.
The next issue of the series, Dark Knight III: The Master Race #4, is currently listed for April 27, after being originally solicited for March 16. The April-solicited #5 is now listed for June 29.
And for some of the final "New 52" titles before the Rebirth relaunch, their final issues are being cancelled completely. Batman/Superman #33, Batman/Superman Annual #3, and Superman/Wonder Woman #30 were originally put into Diamond's system for a June release and included in the first June 2016 checklist the publisher released along with the solicitations, but were removed in subsequent updates.