Anything from 15 minutes to 15 years.
Something happening sooner or later is very likely to actually occur, although at an unknown point in the future.
If it's a bad thing, it is more likely to happen sooner.
If it's a good thing, it is more likely to happen later, and in some cases, never.
This is because of the fact that the universe is striving towards thermodynamic equilibrum. See entropy.