The last version of Gnash, Gnash 0.8.10, was released at the end of January 2012. Up to that point the releases were spread less than one year apart, but now we're without anything new in hand. The latest news on Gnashdev.org as the development site for this project hasn't seen an update since mid-2011.
Fortunately, Gnash development isn't completely stalled. The Gnash Git repository is seeing a commit or two every couple of days. Since the last point release one year ago there's been over 150 commits. (There's also a few mailing list posts per month to gnash-dev.)
Most of the commits are minor in nature but among the items that caught my attention while scanning the commits are some GCC 4.7 compilation fixes, a bit of work on Android, work on the OpenGL ES 1.0 renderer, IPv4/IPv6 improvements, and other changes scattered throughout but it doesn't look like a Gnash 0.8.11 release is imminent.
Sadly, this isn't the only Free Software Foundation high priority project in trouble. These FSF high priority projects are notorious for not progressing.
For those looking towards an open-source Adobe Flash Player alternative that is released more often and developed a little bit more vigorously to incorporate modern SWF functionality, I'd give much more praise to Lightspark. Mozilla has also been working on the Shumway project as an open-source SWF run-time for their browser. Google meanwhile is maintaining their Adobe Flash implementation in Chrome.