Final Cut Pro 10.0.1 release today. One of the most exciting features is xml import and export. That may make FinalSub working with Final Cut Pro X. We are working on it.
Rich XML Support
Now you can import and export Final Cut Pro X project and Event information via a rich XML format. XML interchange enables a wide range of third-party workflows, including high-end visual effects, color grading, and media asset management. Blackmagic Design’s DaVinci Resolve, Square Box System’s CatDV, and many other third-party applications will offer XML-based workflows with Final Cut Pro X.
Apple Link: http://www.apple.com/finalcutpro/software-update.html