I’ve noticed this issue as well.
I manage Flexible Posts Widget. While testing for 3.9 compatibility today (against Beta 3) I have found that none of the admin-enqueued styles or scripts are getting loaded and the localization variable doesn’t get added either.
If you want to test against my plugin, please use the TRUNK version. The current release version (3.2.2) has some if checks inside the script enqueue that are too limiting. (I had been enqueueing the scripts & styles on the widgets.php page only.)
Thanks for the report, DaveE. I’m looking into this.