Well .net still has several languages (even created by microsoft) VB.NET ( less pupular than vb6 was, but still refuses to die inspite of microsofts rather loud signaling that they wish it to) and F#. So yes having c# and .net as separate communities still makes sence IMHO, but I might be wrong
Edit: And i forgot another pont in favor of keeping csharp and dotnet separate, because uf the blackout of r/csharp and the mods hepull linking to this community we are going to see quite a few people coming over here looking for a drop in replacement and they are used to a dedicated csharp community. it would be easier to retrain their musse memmory if they get “the same content at a different url” so to speak rather than a mixed community for all dotnet.

No hard redirect dot net has more languages than c# so IMHO there is a need for a separate community dedicated o c#, at least until the blackout of /r/csharp ends, a few weeks aftre that point it might be a good idea to see if the communeties over here stil are active enugh to vorrent them being separate.