You can find different positions explored in Those Who Have Never Heard: A Survey of the Major Positions . It’s by a Mormon academic, but limits the positions to traditional Christianity.
It explores the positions of:
Universalism
Inclusivism
Postmortem Evangelism
Universal Opportunity before Death
Restrictivism
And it echos this question:
Porphyry, a third-century philosopher and critic of Christianity, asked: “If Christ declares Himself to be the Way of salvation, the Grace and the Truth, and affirms that in Him alone, and only to souls believing in Him, is the way of return to God, what has become of men who lived in the many centuries before Christ came? . . . What, then, has become of such an innumerable multitude of souls, who were in no wise blameworthy, seeing that He in whom alone saving faith can be exercised had not yet favored men with His advent?”
And here is the conclusion:
This paper has provided an overview of the main positions in the history of the church regarding the possibility for salvation of the unevangelized. None of the views is new on the theological scene. Each is a response to the soteriological problem of evil: how can God be said to desire the redemption of all people and yet Jesus be the unique and particular savior of humanity? Positions range from universalism to restrictivism with each view drawing upon scripture and theological argumentation. Clearly, Christians have never been of one mind on the matter, and I doubt we will be anytime soon.
It’s interesting to see what he said of inclusivism - the position I run with:
“The inclusivist position has a long and distinguished history in the church. Such widely divergent thinkers as Justin, Thomas Aquinas, John Wesley, C. S. Lewis, and Pope John Paul II have affirmed it.[40] Today, it is the dominant view of the Roman Catholic Church and of mainline Protestants. Though the Eastern Orthodox Church has no officially sanctioned position, the inclusivistic views of Justin and other Greek fathers are widely cited with approval and many of the arguments for inclusivism are employed.[41] Inclusivism represents the closest thing to a consensus among Christians today.”
If I read Rob Bell’s (i.e. Love Wins) position correctly, he seems to be implying God’s continuing efforts to save folks - after death. This is consistent with visions from Tiffany Snow, the Old Catholic Church mystic and stigmata bearer. Even though I side with inclusivism, I don’t rule this out - as a secondary position.
Those Who Have Never Heard: A Survey of the Major Positions has this to say: