What Bethesda did, they could undo.
They could, yes. But they won't. Umbra's use and destruction was a key part in the novels, they can't just say it never happened. The effects of the novel are shown in Skyrim, with the Dunmer refugees from Morrowind, after Red Mountain blew up,
Umbriel The Ministry fell on Vivec, Mede's taking over of the Empire.