Droid X devices will be receiving an OTA update, version 4.5.605, starting today, September 19th. Supposedly, the update will not work if you are rooted. Also, the update only has one fix, a keyboard bug, even though it is a 113MB download, so keep these things in mind if you want it.
Source: DroidXForums via MyDroidWorld and VZW DroidXUpdate4.5.605.pdf Doc