The 20-year old has had a rewarding season at West Brom, scoring 17 times, and he is set to return to his parent club in time for pre-season.
The Belgian is still wanted back at The Hawthorns for another spell on loan, while West Ham are also reportedly keen on the former Anderlecht frontman.
Lukaku only managed eight league appearances for the Blues in his debut season and the Belgium international admits he would be keen on a move to the Champions League finalists.
"I'll start the season with Chelsea then I will speak with the management to discuss the best choice. I am a realist," he is quoted as saying in The Sun.
"I still need to grow and for that I need to have time to play during the next season. Dortmund would be a good choice."