It would be useful to announce new MediaWiki releases with blog posts at the Wikimedia Blog as well. Currently we only have announcements to mailing lists and a mention in the mediawiki.org homepage. A blog post sounds like a sensible improvement for 2015 ;) that would also make it easier for promotion in our social media channels, which are well synced with the Wikimedia Blog.
New major releases definitely reserve their own blog post. The content is already produced for the related wiki pages, and having only two major releases every year the Comms team surely will offer help improving the post and promoting it adequately if there is a bit of coordination in advance (not a problem since the release dates are usually estimated in advance).
For point/security releases a blog post would still be convenient, requiring only the same content added to the mailing list announcement, nothing fancy.
Another motivation for this request is that the future mediawiki.org homepage being proposed would pull news directly from the Wikimedia Blog - Technology category, which would be an improvement over our current archeological approach with News via wiki templates. This means that whenever that new homepage is implemented, you would only need to publish the blog post, and the news would show up in the homepage automagically. Amazing XXIst century!