It seems to me that it's the other way around. Bellingham is (ideally) a long-term project, so the sooner they start it the better. Plus, the team is not a car where you can change some spare part at one moment and move on. Modric will not last the whole season, and as I say here, you can’t wait that it will be like that: Modric finish and Bellingham will immediately continue. Ideally, he should start playing at Real Madrid next season. Plus, if you wait another year, then you can wait until Bellingham changes his mind and moves to another club.
That depends on what kind of aggrements that will be reached by real madrid and dortmund. As you can see that if dortmund puts very big clause release for bellingham. This is making real madrid is looking for alternative solution to make sure if the club will not pay a lot of money just for him. Jude could be a replacement for kroos. Modric is still saying at madrid till next season as perez has been directly offering him another year to stay on madrid. Madrid is not yet sending its first offer for dortmund.
I will be so hard to reach an agreement if dormtund will still try to peg with its old clause release for bellingham. 150 millions are not small money. Perez was also thinking about that.
Let's wait for what kind of offer that will come from real madrid.