Extensive my ass. Nintendo had a good reason to make an HD port of WW, because it's 2013 and no one with a 1080p TV wants to play a 480p game on it.
The ONLY reason that port was even made was to fill a game slot that was currently empty and make money. Lets not pretend it was because folks wanted to play it but their eyes would bleed to see a 480p game on a 1080p tv. I'm going based off this interview. I'm not going to initially assume they are lying about all their improvements.