Should we apply future perfect or future simple here?

"But I suspect in ten or twenty years' time their situation will change / will have changed".

My language teacher says it should be future perfect here, but I am not sure, because it does not mention a certain point in the future. And there is no sense of completion here either.

  • Compare: Tomorrow evening they will leave and Tomorrow evening they will have left. The first is looks forward from now to their leaving the next day; the second looks back from the viewpoint of tomorrow evening when they will already have gone.. Both are correct. May 5, 2022 at 16:04

1 Answer 1


"In ten or twenty years' time their situation will change" means that the change in their situation is taking place in ten or twenty years, while "their situation will have changed" means that by the time ten or twenty years have passed, sometime beforehand their situation changed. Which one you should use depends on which meaning you intend.

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