Nope, nothing official yet. Well, at least at mainline. The company has publicly stated that the 50-seaters are going away.

But there's plenty of informed speculation based on what the company said they would do if required to downsize. The current displacement would appear to suggest the ability to downsize the 777, 756, and 320 fleets if demand does not recover. FWIW, despite the downturn the 787 fleet in actually growing by 16 frames by the end of 2021.