Really, you think he didn't know what he had planned for that story thread? I think it's pretty darn obvious that he did. I don't think for one second, once he knew that he was going to get to do the trilogy, that it was all done on the fly. I think the end of TESB is crystal clear, in hindsight, with regards to both Leia being the other and Vader being dad.

I agree that this edit won't touch it; indeed, why would any edit want to? There's absolutely nothing wrong with the structure or plot in Empire. It's testament to how strong a film it is that there is so little to change. Updating special effects is no indication of the film being flawed, rather it's just an indication of the technical capabilities of the time. Effects aside, I don't think Empire needs touching.

Just don't get me started on Jedi!