I suspect most of you follow the Wikimedia Foundation blog, but in case you don't:
https://blog.wikimedia.org/2012/04/12/mediawiki-1-20wmf1-deployment/
The bit that will affect your communities from now on:
"We plan to deploy the latest software every two weeks. Rather than calling each version of the deployed software 1.20, 1.21, 1.22, etc every two weeks, we'll be using a variation of the "1.20" moniker for the next few months.
"We’re decoupling our deployment process (to Wikimedia sites like Wikipedia) and our release process of standalone MediaWiki installer for use on third-party sites. We plan to have MediaWiki 1.20wmf1 and 1.20wmf2 in April, 1.20wmf3 and 1.20wmf4 in May, etc., until we actually release a new MediaWiki 1.20 installer this fall (probably October)."
Hope this is useful.