In the latest update for FCP X, Apple included a new feature called roles. This allows you export only certain selections of your footage and audio (dialogue, sound effects, etc.)
Micha Schmidt posted himself working with roles on his latest project. He was looking to find if exporting roles could replace replace using OMF. He ends up finding that OMF may still be the best option but with new update it should only be a matter of time before a third party releases their own OMF exporter.
Thanks to FCP.co for the heads up.