Samsung confirmed to Amateur Photographer that the 300mm f/2.8 lens “leaked” inside an official Samsung video is a working prototype. And a spokesman for Samsung’s head office said that “there is no definitive plan to launch this lens into the NX system“.
P.S.: A beta tester of the NX 60mm/f2.8 Macro lens posted quick review with some pictures: http://www.slrclub.com/bbs/vx2.php?id=newproduct_samsung&no=2737