When you need to convey a sense of delay or a lack of urgency, there are several synonyms you can use for the phrase "not immediately." One option is "not right away," which implies that something may happen eventually, but not at that moment. Another possibility is "not soon," which suggests that there may be a considerable delay before something occurs. If you want to indicate that something is on hold or in a holding pattern, you could use "temporarily deferred" or "postponed for the time being." Other options include "delayed," "deferred," and "put on the back burner." Ultimately, the synonym you choose will depend on the specific context and tone of your communication.