1. yes, upgrade. it'll be a big improvement in picture quality and future proofing(if you like smart features, 3d, etc)
2. this may be the last chance you get to really 'upgrade' until oled is perfected. that could be 5yrs, that could be 10yrs, who knows. point is, you need to ask yourself if the extra couple hundred bux for the 65" will be something you wish you spent later on. i've been there before, where i've bought a cheaper model because that's all the money i had, and then 6months later i've got 300bux in my bank account, and i wish i could trade in what i bought for the better model. it's something worth thinking twice about anyway.
Displays: Samsung PN64F8500/JVC X35
AVR: Pioneer VSX-1018AH, 5.1 audio
Sources: HTPC(Mediabrowser), PS3, XBOX360, Wii, Sony DVP-CX995V
Control: Harmony One