Few days back Mark Jaquith announced that Post Formats UI is exiting WordPress core in 3.6 but it will live as a plugin. It is said that Post Formats was holding the release of WP 3.6 so now developers are planning to extract it from the release but it would be live and will continue to develop as a plugin similar to MP6.
Mark Jaquith’s blog post on make.wordpress.org explains everything pretty well. So read it if your like to know more details including Post Format things that will move to the Plugin and things that will still be there in WordPress core.