Best Buy is already supporting Apple Pay in some stores, despite not having formally announced a start date, various anecdotes indicated on Thursday.
In April, Apple announced that Best Buy would begin supporting Apple Pay in late 2015, but since then neither company has been more specific. Until August Best Buy was restricted by an exclusivity agreement with MCX, the consortium developing a rival payment platform called CurrentC. That system was supposed to go live in 2015, but may now have to wait until 2016.
Apple Pay may not be ready in all Best Buy locations, which would explain the lack of a formal announcement. Often Apple Pay will begin working at individual stores as a partner chain upgrades each one with NFC terminals.