I started looking at F# because of .NET Core, and I'm really liking it. I currently use Giraffe in a project, but I'll be switching it to Saturn soon (which uses Giraffe under the hood). And I've identified a potential use case for using Fable on some already written server-side code. Ionide is great, Neptune (F# debugger for VSCode) works well, and they both are maintained by the same person as Saturn.
Rider also works pretty well with F#, which is nice if you prefer the JetBrains IDEs.
* "Official" Cross platform support -> dotnet core FTW!
* Cross-IDE intellisense support -> Ionide, Check!
* Dotnet core support -> Check, finally(and make sure to set Ionide to use core)!
* F# to javascript cross compilation project with some traction -> Fable, check(Fable needs serious documentation help though)!
* A great framework competing head on with Phoenix -> Hopefully soon :)
The potential just seems sooo massive. Hopefully it blows up quicker than Haskell ;)