Per the DMN blog, Tommy Hunter and Travis Metcalf are up, Ryan Roberts is down, and Eric Hurley has been put on the d.l.
Kason Gabbard has been moved to the 60 day d.l. to make room for Hunter on the 40 man roster.
The only other 40 man move that would appear to be imminent is bringing Brandon McCarthy back from the 60 day d.l. At that time, you'd figure either Hank Blalock would head to the 60 day d.l. (if he isn't coming back), or Ryan Roberts would be DFA'd.
Or who knows...Frank Catalanotto could be traded by then, or one of the myriad of hurt Ranger pitchers could turn out to have a season-ending injury.