Wikimania. One talk was about Semantic MediaWiki and the other about Open Street Map. Both are great subjects for a MediaWiki conference because both add important functionality to MediaWiki.
When you think about it, it would be really cool when the results of a SMW query that results in geo data is presented in a map. At the moment there are two extensions to SMW that do just that; Semantic Layers and Google Geocoder.
Given that much of the primary functionality can be found in either extension, it should be possible to come up with something that would work for Open Street Map. Having support for both SMW and OSM would present a paradigm shift; it would make it easy to mesh Wikipedia in the big data world.