Currently, he is not part of Mauricio Pochettino's plans and he will not be joining the team for pre-season games in the United States, just as Hakim Ziyech and Pierre-Emerick Aubameyang. The Saudi League would have been the easiest route for him, but Lukaku has made it clear that he is not moving to the Saudi Arabian League so he has to wait to see if his transfer to Juventus will come through.
Juventus are making a mistake signing him, he's a great player but lack the personality of a great player. He isn't loyal to his parent club and easily gets disloyal to any club that he signs to. I won't be surprised when stories of him having issue with Juventus begin to circulate the internet. Saudi Arabia indeed would had been the perfect destination for him but he has already rejected them and it seems him having a club depends on only Juventus to offer him a contract. Chelsea are just fed up with this player and wants to get rid of him as soon as possible. You can see it all over the Chelsea management.
Chelsea wasn't looking for any highest bidder, they had a price tag of Lukaka already and was willing to sell to any club that can match the bid which the club in Saudi Arabia already matched the bid but Lukaku rejected their offer and wasn't willing to go to Saudi Arabia probably because he knew Juventus was coming for him since Inter Milan was finding it difficult to match Chelsea bid and was messing around with offers they were bringing to the table. When they saw that the talks with Juventus was advancing they brought in a better offer but it was already late because Lukaka has lost interest in the club.