time will tell
(idiomatic) Events and outcomes cannot be known beforehand.
This may not be a good idea, but time will tell.
Time will tell us what we did and didn't do. Harvey Fierstein
Well, I think that she's got a lot of Marla [Maples, Trump's second wife], she's a really beautiful baby, and she's got Marla's legs. We don't know whether she's got this part yet [gestures toward own chest], but time will tell... Donald Trump
I guess it's a sequel to our story From the journey 'tween heaven and hell With half the time thinking of what might have been and half thinkin' just as well. I guess only time will tell. Harry Chapin
Right now the Jews are still surrounded by enemies who are sworn to their death as a nation. Their only hope is to turn to God with their whole heart, and if they obey Him, they will have victory. Only time will tell us if they have learned anything from history. Ray Comfort
Only time will tell if serendipity becomes zemblanity as consumers are constantly bombarded by advertisements. Newton Lee
The year that 'Lost' started and premiered was, without a doubt, the most miserable year of my life. The level of despair and anguish that I was feeling; I was clinically depressed, and anyone that you talked to who knew me at the time will tell you that. Damon Lindelof