I think we just have to leave it up to the Lord as indicated in these passages in the Gospel of John for ex. :
King James Version (KJV)
22 For the Father judgeth no man, but hath committed all judgment unto the Son:
23 That all men should honour the Son, even as they honour the Father. He that honoureth not the Son honoureth not the Father which hath sent him.
24 Verily, verily, I say unto you, He that heareth my word, and believeth on him that sent me, hath everlasting life, and shall not come into condemnation; but is passed from death unto life.
25 Verily, verily, I say unto you, The hour is coming, and now is, when the dead shall hear the voice of the Son of God: and they that hear shall live.
26 For as the Father hath life in himself; so hath he given to the Son to have life in himself;
27 And hath given him authority to execute judgment also, because he is the Son of man.
28 Marvel not at this: for the hour is coming, in the which all that are in the graves shall hear his voice,
29 And shall come forth; they that have done good, unto the resurrection of life; and they that have done evil, unto the resurrection of damnation.
There seems to be much room for those who He will determine to have done what is right in His eyes Christian or non Christian. We need to have faith & hope in our own salvation & for anyone's salvation & fear God.