it's only, just, etc. a matter/a question of time

be just a matter of time

To be an inevitability or eventuality; to be or seem sure to happen at some point in the future. With your reckless spending behavior, it's just a matter of time before you go broke. We'll catch the person responsible eventually. It's just a matter of time.
See also: just, matter, of, time

be just a question of time

To be an inevitability or eventuality; to be or seem sure to happen at some point in the future. With your reckless spending behavior, it's just a question of time before you go broke. We'll catch the person responsible eventually. It's just a question of time.
See also: just, of, question, time
Farlex Dictionary of Idioms.

it’s only, just, etc. a matter/a question of ˈtime (before...)

used to say that a thing will definitely happen in the future, although it may not happen immediately: Don’t worry, you’ll get a job if you keep looking. It’s just a matter of time. It’s only a question of time before the fighting spreads to the city.
See also: matter, of, question, time
Farlex Partner Idioms Dictionary
See also:
  • be just a matter of time
  • be only a matter of time
  • be only a question of time
  • be just a question of time
  • only a question of time
  • a matter of time
  • a question of time
  • be a question of time
  • a matter of (something)
  • a matter of days, miles, pounds, etc.