There was talk of notes in some interview(s) waaaaaay back when they were getting into their Butlerian Jihad trilogy, or maybe it was just before they were going to write/release Dune 7.
But it was clear they were full of shit (either on whether the notes actually existed, or whether the notes were actually being followed) whenthe old Face Dancer couple from Duncan's visions unmasked and were the ROBOT VILLAINS ALL ALONG! THE ONES WE MADE UP IN OUR DUNE/TERMINATOR FANFICTION TRILOGY!!!!!! ROBOTS ARE BACK BABY!
EDIT:
Maybe they thought ROBOTS! was a better idea because, like, you can't enslave robots with your superfuck skills. Lolol.
EDIT MORE:
Of course, even if one assumes that somehow Frank intended it to be ROBOTS ALL ALONG (lol), the hacks probably didn't need to write a whole fanfiction far prequel trilogy just to set it up. Frank sure as fuck didn't.
Robots eh...I always envisioned them as Tleilaxu but like in a similar situation to the Honored Matres