I would imagine it was something more mundane like a simple issue of not getting copyright approved in time. It's part of the reason why we've never seen Tarzan after the first game because even Disney technically doesn't own the full rights to the story.

In the case of Pocahontas, I would imagine it's simply a matter of avoiding controversy since, unlike every other Disney property, she was a real person. Not to mention all the damn controversy that came about when the original film came out. I would imagine that particular film is off the table due to Disney and SE not really wishing to alienate any fans.