It’s hard to say as Steven Spielberg said in a 90’s BBC special that part of George’s concept for the Prequels was the Sequels. He also slipped up in an interview during the lead up to Attack of the Clones where he mentioned story points in II have to connect with VII.
Sources?
“The challenge for me is telling a six-part story: so in Episode I there are things that I have to get in that refer to Episode VII… no, hang on, we’re not there yet. I mean Episode IV.”
https://www.theguardian.com/film/2002/may/15/news.seanclarke
Correction it was Episode I plot threads in Episode VII. It does show he had a plan of sorts. Nothing fully definitive but I can definitely see plot lines that tie into things he talked about for his Sequels. I think he always had a broad idea of where he wanted to take the story. It’s just the details that needed to be worked out. The Sequels were always less fleshed out than the Prequels.
As far as the Steven Spielberg (Rick McCallum too) bits:
3:42 minute mark.