3D technology and Video Resolution (SD, 2K, 4K, etc) are totally independent and separate. Supercharged will use the same Polarized 3D technology as King Kong and Shrek, but the resolution of the footage will be higher at 4K and use the most top of the line projectors. To update King Kong (if it is in fact 2K instead of 4k), they'd need to go back to the source footage and remaster the footage in 4k, and then update the projectors as well. "Simple" but would take a bit of time for remastering, installation and recalibration.
Although to be honest, I think Kong has maybe been 4K this entire time, as it's still pretty sharp and I've never been able to see "pixelation" that you normally would see in 2K footage. Some resolution just gets lost in 3D due to ghosting and the dim nature of polarized 3D. If Simpsons got to use 4K times four in 2008, I'm pretty sure Kong is 4K as well. I'd be interested to find out from Creative.
I'd really love to see Kong and Simpsons to at least receive brighter projectors.