Firefox 50, which was originally scheduled to release on November 8, this year, has been postponed to Nov 15. Reason for the delay is Mozilla has made extensions built with Add-on SDK to shut down and startup faster than before, for Firefox users with multiple add-ons installed this makes a big difference. To offer these improvements to release channel users, the company has delayed Firefox 50 release. If you don’t have multiple extensions installed, then you may not see the difference.
The new version of Firefox to come with following new features, changes and improvements along with the one mentioned above.
For more information, check Firefox 50 beta release notes.