I have read many prototype screenplays of ROTJ and Star Wars in general, and I contend that he intended to make somewhere between 9 and 12 episodes as a kind of serial, and had no intention of making prequels whatsoever. I think the closure of ROTJ pretty much sealed the deal, making it *almost* impossible for sequels. I think he thought he was done with it, and then later on he was compelled to revisit Star Wars, and had no option but to either make prequels, or an entirely different trilogy. But who knows?

Skyjedi, also in that early ROTJ script, the Emperor takes Luke to a kind of Tomb, where Obi-wan returns from the Force 'netherworld' to help Luke. I think you can find it on IMSDB.com.