Greater symbolism spoilers!
I'm thinking the ending might be a symbolic part of a film elaborated earlier when John met the sister. She said something along the lines of "are you afraid of damnation?" And referred to Wick as Deaths apprentice or something like that. Winston has a strange moment where he gets literally everyone to stop with a simple text almost instantly. I'm thinking the symbolism is that Winston is in fact the devil himself, and damnation (3rd movie) is coming. This is why the last scene shows John running completely scared,