That's not as easy as you might think, but I'll tell you what I know.
For 2009, Mits claimed to have rev'ed to 5th generation ("5G") several PQ-related features. Plush1080p (upscaling), SharpEdge (Edge Enhancement), DeepField Imager, and Video Noise reduction.
However, as skeptics point out, they provided no proof of having done so (side-by-side screenies, or whatever), reviews don't seem very clear on the point of whether they saw an improvement, and various folks who have seen both don't seem to see it.
I think Smooth120Hz (blur reduction, not 5:5 pulldown) is available on the entire model line for 2009 --I believe some lower model 2008 did not have it. Some have suggested they really did it because it is a 3D-enabler as well, and by putting it on all the models they got to claim that their entire lineup was 3D-ready.
They moved most (all?) of the advanced PQ-tweaking options out of a system menu and into a user menu. That seems nice if system menus intimidate you. But I know at least one guy who swears that he had better ability to tweak the color accuracy on a 2008 with the old system menus than with the new 2009 user menus. So, that could cut either way depending on what kind of owner you are.
For the 837 models, they also added the ability to save two separate sets of advanced PQ options on the user menu --intended to be used one for daytime viewing and one for nighttime viewing.
So there ya go.
Given that there has been a PR announcement from Mits already re the 2010s, I would be very surprised if they pulled out a last minute PQ-increaser that they failed to mention in that PR. That would be very strange marketing indeed. At least one of the features mentioned above is referred to as "5G" in that PR, which indicates it is the same as the 2009, and suggests the others are likely to be so as well.