Isak won't make official statement about leaving Newcastle until his current club will able to find his replacement. However, he's in stance to leave from the club. I saw the latest rumor says his club targets Jackson as his replacement, but still waiting for more concrete news to come. If his club successfully sign Jackson from Chelsea, he can leave.
He can only leave in two cases: if Newcastle allow it (on terms Newcastle agree) or if he pays a release clause to end his contract early. What he wants or doesn't want, or whether Newcastle signs someone or not is irrelevant. Isak has a contract until 2028, so he is obliged to fulfill it or come to an agreement with Newcastle. As I understand it, now all interested parties are waiting, but Newcastle is in a better position because even if Isak's transfer does not happen, they are satisfied with it.