My problem with the ending (spoilers, duh)
I see two options.
1. Winston betrayed John Wick. Problem: that doesn't fit Winston's character. He's a man that lives by a code, a man that always does what's right. Of course, his idea of 'right' can include being cruel and cold-blooded. But I don't see how betraying Wick, a man he considers almost as a son, would make any sense. That would be out of character.
2. Winston didn't betray Wick, it was a hoax. That would be possible, but... problem: the hoax includes Wick falling for a 5 stories building.
Even in John Wick's fantasy universe falling from a building would surely kill you. Wick survived, because of plot armor, and we'll have Wick 4. But characters can't count on plot armor, they don't know they're characters in a franchise (unless you're Deadpool).
None of both makes any sense. I guess they included that fall because, hadn't it been included, it would be too obvious it was a hoax. I think they made it worse, though.