IMO we're going to likely struggle to sign a top rated / elite level CF if we wait until the summer. Primarily because we are not in UEFA to compete with the EURO Elite, and because Arteta does not have the credentials of the likes of Pep, Klopp, Rangnick, Tuchel or Conte in the EPL. Just as importantly we need the goals this season in order to secure top4, and more so with both PEA and Pepe on the outer with Arteta.
Then there are the likes of Barca, RM, PSG and potentially Bayern who may all be looking for new CFs sooner rather than later. Things get further complicated when we have top clubs like Barca who are skint and they are looking at the likes of Cabral and others from the next levels below the elite, along with NUFC who have the money and the need to join the elite.
About the only advantage we may have is EPL revenues in the post-COVID market. IF we were able to come up with the money I'd not wait until the summer and would consider going BIG/hard at it in Jan, particularly if we are sitting in top4.
For the prices being talked of for the likes of Vlahovic, Isak, DCL etc they are equal to or more than he reported release clause for Haarland next summer which is reportedly between 60-80m, and that would be my bench mark in terms of transfer fee.
Accordingly I'd go to BVB and put 80-100m on the table now. I'd offer Haarland a 5 year deal but would also include release clauses for him to leave under certain circumstances if we do not match his ambition/success after at least 2 seasons. IMO at the very least it would show serious intent/ambition regardless if we were successful or not, and that may help in negotiations if we need to look elsewhere.