Bernardo hasn't really gotten time ahead of Sterling though. If you're naming our best XI with everyone fit, Sterling is in it, not B. Silva who definitely played second fiddle, starting half as many league games as sterling (29 vs 15).
I think there might potentially be a chance that Sané gets a bit put out if we go and buy Hazard because if he comes, Hazard is going to play every game or near enough. He'll be like KDB and Silva - he'll have a regular spot in the starting XI and Sané may get relegated to a similar role to Bernardo's this season, or best case scenario a 50/50 share like Aguero/Jesus.
It'll definitely be a change for Sané, he may have to move around more to get games, he might start seeing a lot more sub appearances rather than starts, he will find that he's not immediately in that starting XI for the first time since December 2016 really, and that might cause problems.
At this point however, I think we just have to trust Pep to get it right, manage the squad to keep them happy and to make the right selection decisions.