If I am Lukaku, I will move to Saudi and forget about playing in England or Italy since there is no good deal done for him next season. Lukaku needs a place to call him and not moving from one club to another on loan. SPL will be beneficial for him with the huge pay and he will retire successful.
Due to Lukaku current age, I don't think that there is much for him to achieve again in big leagues but having a good club that respects your presence and pays well is a good retirement plan. However, it is not all players that will love to move down to SPL, so the choice is left for him to make.
He is still reluctant to do that because if he really intends to join the SPL from last season he can also do it because if I remember correctly before deciding to go to Roma on loan, Lukaku was previously tempted with very large money from the SPL club but Lukaku insisted not to do that.
Now Conte wants to try a reunion with Lukaku at Napoli. This is still quite doable, it's just that the obstacles that occur at this time are always based on the clause from Lukaku which is considered too expensive.
In addition, the rumors now actually Lukaku also expects to return to domestic competition in his current country because it is rumored that Lukaku wants to go to Anderlecht even though this is still a pretty hot rumor for Lukaku.