From my reading of the interim accounts commentary it sounds like cancellations and uncertainties will last well into 2020. There is an interesting comment which appears to suggest IAG sees things starting to return around July:
IAG is planning a meaningful return to service in July with a planning scenario that could see an overall reduction in passenger capacity of c.50 per cent in 2020, but these plans are highly uncertain and subject to the easing of lockdowns and travel restrictions
https://www.iairgroup.com/en/newsroom/press-releases