Saul mentions an "Ignacio" - which "Nacho" is a common nickname for - in his first scene in BB, but I do not recall exactly what he says about him.
He doesn't say much, but I think the quote is, "It wasn't me! It was Ignacio!"
He also asks, "Did Lalo send you?"
With the current Lalo stroyline overlapping with the BB timeline, I think we might see a bit of that overlap on screen.
We also need to know what happens in the flash forward! Major cliffhanger to start the season.
I also think that the flash forward "Gene" scenes will get a little more play. Jimmy is the only one left to pay for the crimes, I believe.
I wouldn't be surprised if at some point there is a prequel series about Gus either.
I just finished a BB rewatch, and during the 4th season, his past and name change circa '86-'89 was mentioned conspicuously more than a couple times.
Which would be fine with me. I've enjoyed the universe thoroughly, and as of now, both series and the movie have been better than decent to awesome.