In most cases, even after changing a dataset, your cancelled journeys will continue to be cancelled.
The following conditions are required for this to happen:
The new dataset contains journey IDs that have not changed from the journey IDs used in the dataset that was 'current' on the date the cancellation was made.
The times of the stop visits for those journeys have not changed.
If either of these is no longer true, you will need to create a new cancellation to ensure the journey does not appear on departure boards/journey plans.