Given I got the Faces trilogy when I was probably 4 I don’t think much of what Maltin and Lucas were discussing sank in with me at the time. It actually probably wasn’t even until the prequel era that some of what they were discussing I began to pay attention too and I suppose it was around that time I started noticing the preview discussion of the PT.
Most of it is at the end of the ROTJ interview. Lucas mentions that he’s working on them all at once and that the first would be out in ‘98 or ‘99. Maltin concludes with something like “so in the new millennium we can look forward to the prequel trilogy??” to which George says “definitely”.
Technically George’s message on the outer box of the Faces set makes a subtle reference to the PT coming up when he says something “I hope you all will continue to not only enjoy this Trilogy but the upcoming events in the continually unfolding Star Wars universe” or something to that effect.