OR another way of looking at it is they can share game time and provide competition to one another to improve themselves. Like you alluded to, they are still young and will be inconsistent. Putting some competition in the team will help them to remain grounded and keep them aware that they could easily lose their place any time if they don't perform. Furthermore, if CHO goes to Bayern, for instance, does he really think he will start week in week out? If anything, I'd be more concerned if Willian/Pedro (hopefully the former will leave!) stays on because they would likely see a lot of game time and especially with Sarri's stubbornness of sticking with him.