Question: My probationary period passed three days ago, I have not been told if I passed it, and I have my evaluation early next week. Should I assume that I have passed probation?

Answer: 
Judging by the fact that you haven't been let go, I'd say you pretty much have but I'd wait for an official word from your manager or someone higher up. Usually you should be invited to a meeting to discuss your performance.
I can't see why they would have that conversation with you *now*. They're doing an evaluation next week, and that is the ideal place for that conversation. 

I would expect them to tell you then. In the meantime, bring your A-game.