I don't know what plans Chelsea have for replacing Lukaku but Christiano Ronaldo moving to Chelsea seems very unlikely. He wouldn't do that to Manchester United. Lewandoski might be open to a move to Chelsea and with his price tag Chelsea are in a better position to get him than Barcelona at the moment and I think he will be open to the idea of moving to the English premier league.
Previously Chelsea want to bid Richarlison and I thought he will replace Lukaku position, but there's a news if Richarlison is prefer with Tottenham. Chelsea are looking for many midfielders and backs, but they don't consider to get new strikers. If there's no new strikers, then Chelsea's strikers will be Kai Havertz and Christian Pulisic. Lewandowski have a personal agreement with Barcelona, he wouldn't move to another club.
But if Bayern don't want to let Lewandowski go, why are there rumors and discussions about him so far?
Bayern Munich want to let Lewandowski go to Barcelona, if Barcelona can pay the fee that Bayern Munich demand.