1
general::
Eventually, at some unspecified future time, as in Sooner or later we'll have to answer that letter, or It's bound to stop raining sooner or later. This term, which generally implies that some future event is certain to happen, was first recorded in 1577.
American Heritage Idioms
2
general::
Phrase(s): sooner or later
eventually; in the short term or in the long term. • He’ll have to pay the bill sooner or later. • She’ll get what she deserves sooner or later.
McGrawhill's American Idioms And Phrasal Verbs