Well, I could go dig up a bunch of quotes or I could just tell you that tradition says that God is the Judge, not us.
ITT: People who think they know how God is going to judge humanity.
Keep up that arrogant thinking, but we all know what the tradition really says.
And what does it say?
I think there's some confusion here. William is quite right that the Bible and Tradition tell us who will be saved: "except a man be born of water and the Spirit, he shall not enter into the Kingdom of God" (John 3:5). So as far as we know, we must be baptized in the true Church and remain faithful to the Church to be saved.
You rightly say that God is the judge. Only God knows the secrets of every heart and who was truly faithful to Him and who was not. So with respect to other people, we cannot usurp that judgment. At the same time, since God has clearly told us what we need to do and believe to enter the Kingdom of God, we can't abdicate the responsibility to tell this truth to others.
What you have to ask yourself is: "When I talk about how God is the judge and not myself, am I saying this just to get out of the difficulty of telling the truth to others?" It's not exactly fashionable these days to believe that only one way is the Truth, so the temptation to flinch from telling this truth is strong. I myself have not always been good at witnessing.