Yeah you're not wrong for sure. It's like when even before Hazard joined Chelsea he was one of the best dribblers in the world but that didn't change at all when he changed league, his numbers actually improved as he aged. Bernardo Silva still goes passed players with ease in the Prem. It's more of a can he continue to create the same number of chances for goals etc as they did in their previous league which definitely applies to Keita. When you're a world class dribbler the league won't affect your dribbling much it's just whether you can continue with creating chances, assisting etc. And with Hazard, Bernardo and Keita I think Ligue 1 defenses are much poorer than Bundesliga but at the end of the day Keita is still young there's no guarantees he won't flop so like you said let's just wait and see.