The problem I see when going from 60" to 65" is the enormous price increase, greater than any other increment, ie. 55" to 60", etc. The latest I see on the GT50 series going from 60" to 65" is $600!! To me, not worth it. I bought the 60GT50. But as a disclaimer I just sold my 65VT30 and now have a projector on a 130" screen so if I want big I go into a different room now. But aside from that, I am not feeling any loss from my 65VT30 to my 60GT50. YMMV.
Also, if you can wait, Panasonic will have a plasma greater than 65" in 2013, all but directly confirmed over at HDJ.