If Haaland leaves Dortmund in January, it will be difficult for Dortmund to find a place in the top four of the points table. The Dortmund team has become overly dependent on Haaland. They haven't even found a talented player to replace Haaland now. So it will be more difficult for Dortmund to score if they leave Haaland. Moreover, their defense is not very strong. So Dortmund should try to keep Haaland in the team this season.
I don't give much chance for Erling Haaland to leave Dortmund in January already. And we don't even know if Real Madrid or some other team will make an offer for him. I think that Haaland would would like to wait until the end of the season to make his final decision. He must be happy with his game for now even though Dortmund are not in a very ideal condition. But in the next summer, I strongly believe that he will leave the team to join a bigger team like Real Madrid.
Personally, I think Haaland should be leave Dortmund now. And looking for better opportunities. Real Madrid or Barcelona may be waiting for him. Real Madrid will now look for a replacement for Benzema. Haaland is perfectly suited as a substitute for a regular scorer like Benzema. I think Haaland would be more suitable for the Real Madrid team than Mbappe. But everything depends on Haaland's decision. For this we have to wait till January.