Klopp is really taking a risky move by selling their two veteran midfielders, it's similar like Chelsea. Although the performance of both Chelsea and Liverpool in club friendlies are good enough, but we don't know what will happen in the real match.
Chelsea and Liverpool lack of midfielders.
Manchester United lack of strikers.
I would say Manchester City, Arsenal and Newcastle United are shining in this season.
The transfer window is still open, and because both coaches are experienced, they will know whether or not to sign fresh players for the following season after selling some of them to other clubs. Teams who sell players do so due of the manager's decision; if those players cannot fit into the pattern of football they want to play, they easily release them and use the ones that are available, or better yet, look for better replacements for them. If they've been doing well even after selling some players, they should be able to do the same when the regular season begins.