Fedora 21 has already been delayed multiple times, including a three week delay for finishing new features and changes for this huge Fedora Linux release. At this week's Fedora Engineering and Steering Committee (FESCo) meeting there was no further delay but a hope of going into the alpha freeze today and noting that if another delay were to happen it would land on Thanksgiving week here in the United States (2014 Thanksgiving: 27 November). Judging by past release behavior around major holidays, this would then likely slip Fedora by another week and thus put it into December -- well past the original hope of releasing in October.
Anyhow, today's FESCo minutes can be found via this mailing list post and for now the F21 release schedule remains unchanged on the Wiki. In a separate devel post was readying of the alpha change freeze for Fedora contributors.
The Fedora 21 Alpha will hopefully occur on 9 September, the beta release on 14 October, the final change deadline on 4 November, and the official Fedora 21 release on 18 November.