The A65 is an APS-C size sensor, which make the lens like a 600mm. It's still too short. And if the camera was full-frame it would be way to short.
Sony has been talking about the 500mm f4 for three years now. We've seen mock-ups under glass, and other mock-ups under other glass. Now it's the end of 2011 and the lens is still un-released.
I hope to be shooting with this lens in 2012, I just hope Sony plans to bring it out.