Hopefully will grow into a great LB for the club.
Sell off Moreno now, have no need for him in the squad anymore.
Milner/Robertson - LB
Clyne/Trent/Flanagan - RB
Ranking of full backs in Klopp's mind?
Robertson said in the interview (when asked about his goals for the next 12 months) that his aim is to be a starting XI player, and I think he has a very good chance to usurp Milner given that he offers a more natural left-footed option to stretch opponents in a low-block in particular.
That said, it's probably most likely that Milner is the starting LB at the start of the season as Robertson gets up to speed tactically, but as the season progresses I think Robertson will gradually get more responsibility. I can see the Milner vs Robertson question being a common topic of discussion this season, but I'd imagine that Klopp is just delighted to have two competent left backs who he can trust and rotate through the season.
As for Flanagan, might sound harsh but I think he's just on the tour to make up numbers. Klopp wants to play 2 different XI's each half in games, and Flanagan gives the team cover in case one of the other fullbacks are injured or need some rest. I'd be very surprised if Flanagan is still in the squad when the window shuts.