The phrase "be/hang in the balance" means that something is uncertain, undecided or in a state of limbo. There are several synonyms that can be used to express the same thing. One alternative is to say that something is "up in the air", meaning that there is no clear outcome. Another synonym is "in doubt", which implies that a decision or outcome is not certain. Additionally, one can use "uncertain" or "undecided" to convey the same idea. "In limbo" is another synonym that can be used to describe a state of uncertainty or inaction. Lastly, "on the fence" suggests that there is a difficulty in making a decision.