1. the result(s) of a present situation will become known sometime in the future
time will tell if we made the right decision
The phrases 'time will tell', 'time alone will tell' or 'only time will tell' all mean that the result of something will only be established or be made clear at a point in the future. It is similar in meaning to 'wait and see' or 'we will find out soon enough'. This is an informal expression usually used in social contexts or spoken English.