I don't see how the events up to today doesn't tell us that Twitter can indeed survive on a reduced workforce.
There may be growing and adapting pains but, overall, the service is working and not degrading.
The company may very well not survive much longer but I don't think it'll have anything to do with having fired all those devs.
The problematic side was the business side, so if laying of a few thousand people extended the runway to figure things out, it made all the sense. And if it ends crashing and burning regardless, then, who cares?