UPDATE!
4.9 has officially released! Official thread and release notes here: Unreal Engine 4.9 Released! - Announcements - Epic Developer Community Forums!
I’d like to thank every one who helped to test and identify issues during the preview process; we were able to squash a number of bugs that we might not have caught otherwise due to you. Because the preview has ended I am going to close this thread now. If you have an ongoing discussion about 4.9, please continue it in the official release thread.
Thanks!