There were plans.Interesting. A few years ago we had numerous people claiming there WERE legit plans to either expand or restructure Frontierland. Or at the VERY least permanently dock the Riverboat (possibly to turn it into a new restaurant or something). I recall marni1971 insisting that they've been looking for an excuse to perma dock the Riverboat for a long time now. Though I guess they wouldn't need an expansion plan to do that if they wanted.
Last time the rumor got major traction was about 3 years ago. It was @whylightbulb that initially brought it up 2012, and then again in 2015 saying it was finally about to be approved. This was followed up with confirmation from other people like articos, marni1971, MansionButler84, Lee, etc at least saying the project was real.