I've created an RfC page on adding support for partial page caching (edge side includes) to MediaWiki. Please add comments there if you have any thoughts on this: http://www.mediawiki.org/wiki/Requests_for_comment/Partial_page_caching
There is also a corresponding Bugzilla bug here: https://bugzilla.wikimedia.org/show_bug.cgi?id=32618
Ryan Kaldari