As James said here, and on the meta page, we should stick by the wisdom of, "If it ain't broke, don't fix it."
One benefit for each year's Wikimania team is that it has a brand new MediaWiki install, which allows them to have a clean slate technically and design-wise from previous years. It also keeps administration cleaner, and maintains compatibility as we go forward. I've been involved with every Wikimania since the first one, and it would be painful to have to maintain the same MediaWiki instance across a decade's worth of Wikimanias.
I do appreciate opening the discussion to thinking about how to make this cleaner. But unless there is a compelling need, you usually stick with what got us here.
-Andrew