I'd say it is almost pointless to go from a 60 to 65". Hold out for a worthy upgrade, 80"+.
Which means abandoning plasma, too.
If the current 60" plasma is old enough, the *T60 series (2013) models will be a big enough upgrade in PDP quality, especially in the blacks department.
I agree, when getting a new TV, going from 60" to 65" is hardly a worthwhile upgrade for Screen Size, it COULD be a worthwhile upgrade in Image Quality. That's up to the person with the money to decide.
Considering I have a 50", I have only one size in mind as a "worthwhile upgrade" - and that's a moderate-throw projector creating a 10' or larger image.

That would be a sort of dedicated home theater, for sure. Depending on when and where I am when this happens, I'd like to have a large display in such a home theater room, and a drop-down screen that hangs right in front of a "smaller TV" and the front speakers and whatnot. Could be a good spot for the 50", or that could be a living room TV and another TV gets the backup duty in the home theater.
I'd watch movies and play some games on a projector, but for a lot of TV, I probably wouldn't want to waste bulb life on it. And since plasma's will have superior blacks to even the top-end projectors, that's a good backup.
Sorry for the digression. It happens.
