And you base this assumption on what? Something you pulled from your butt? No one knows exactly how many subscribers WoW has to begin with. Nor does anyone know the number of active players divided among each one.
Second, where do you smell desperation? We're at the end of the expansion. Subscriptions normally drop during this time anyways. Is BfA your first time playing WoW? We saw dips at the end of Wrath, Cata, MoP, and WoD at the end. Not to mention the final raids lasted a year or more. Assuming Shadowlands launches on December 31st, that would mean Ny'alotha would have only been open for 49 weeks. And we know that most likely Shadowlands will probably launch sometime around Blizzcon or shortly thereafter.
And Classic WoW is going to run into a harder brick wall... the fact that Naxxramas is the last piece of content it gets. Then it just becomes a sandbox of nostalgia.
This is their equivalent to the artifact power surge at the end of Legion. It is also Blizzard doing what it can to help mitigate what is happening with the 'rona because people still are locked in for safety reasons.