An extended version of "King Kong" is virtually impossible coming from Peter Jackson. I mean, 50% of the movie was filler to begin with, and I highly doubt he cut out any background character development, which it was sorely lacking, muchless anything intrigal to the storyline.
I'm sure it exists, but I fail to understand how there was anything to excise. If he were to go back, restructure it, cut it down, and flesh it out, I'd be all for it...but that's a pipe dream.