C. S. Lewis describes the life of a saved Christian as a “Christ-life” or “new life”. In his book Mere Christianity, he briefly touches on the subject of those who have not been able to believe in Christ:
Is it not frightfully unfair that this new life should be confined to people who have heard of Christ and been able to believe in Him? But the truth is God has not told us what His arrangements about the other people are. We do know that no man can be saved except through Christ; we do not know that only those who know Him can be saved through Him. But in the meantime, if you are worried about the people outside, the most unreasonable thing you can do is remain outside yourself. Christians are Christ’s body, the organism through which He works. Every addition to that body enables Him to do more. If you want to help those outside you must add your own little cell to the body of Christ who alone can help them.C. S. Lewis, Mere Christianity
Thus, trying to figure out what happens to those outside the body of Christ should not be a priority. Rather, we should use what we know (that salvation is through Christ) to reach those outside the body. Anything beyond that lies within the realm of theological speculation, debate, and discussion, but the Gospel is not about the fate of the unsaved.