The simple answer is we do not know. It is not our judgment to make, it is for Christ to judge (John 5:22; Matt 5:31), and so any attempt to say “he’s in, he’s out” would be presumptive and inappropriate. The example of Elijah, who thought that he was the only one who had remained faithful, warns us against assuming that we can know now the true extent of those who will be saved (Rom 11:2-4). If we were to boldly proclaim that “only Christadelphians will be saved” then we would undoubtedly be proved wrong by the saving power of Jesus Christ.
Whilst it is not for us to make the judgment, the Bible does give us guidance about who will be saved. For example, when asked “what must I do to inherit eternal life?” (Mark 10:18) Jesus responds with an injunction to keep the commandments and reject worldly riches (Mark 10:19-22). When a lawyer asks Jesus the same question, the answer is to keep the two greatest commandments: “You shall love the Lord your God with all your heart and with all your soul and with all your strength and with all your mind, and your neighbor as yourself” (Luke 10:27). When the Philippian jailer asked “what must I do to be saved?” Paul and Silas respond that he must believe in Jesus (Acts 16:30-31). Similarly Peter says “there is no other name under heaven given among men by which we must be saved” (Acts 4:12).
Elsewhere in the Bible we are given other indications about the basis on which the judgment will be made. Those who will be saved will do the will of God (Matt 7:21), will be baptised (John 3:5; Mark 16:16) and will not act immorally (1 Cor 6:9; Gal 5:21; Eph 5:5). And repeatedly we are told that we are saved through God’s grace and our faith (Acts 15:11; Rom 10:9). Looking at all the passages that speak of who will be saved and who will not, the repeated message is that those are saved will have faith in Jesus and will demonstrate that faith through love.
There are very few passages in scripture that indicate that the judgment is made on the basis of what doctrines we hold. Hymenaeus “made shipwreck of [his] faith” (1 Tim 1:19) by denying any future resurrection (2 Tim 2:17-18); clearly one cannot expect to be saved if one does not believe in salvation. Similarly Paul criticises those who denied the resurrection of Jesus, saying “your faith is futile and you are still in your sins” (1 Cor 15:17); clearly one cannot expect to be saved if one denies the means of salvation. For this reason John says that those who deny that Christ has come in the flesh are “antiChrist” (1 John 4:1-3). Some beliefs are necessary for salvation – namely, one must believe that one can be saved. Apart for these passages, I do not know of any indication in scripture that certain doctrinal commitments either will keep one from the Kingdom or are essential for salvation.
Truth is important. Those who love God will love truth, and will earnestly seek to know the truth about God. So doctrine matters inasmuch as it is truth about God. However the Bible indicates that the judgment will be made on the basis of faith and conduct; there is little indication that assent to a long list of doctrines will be a prerequisite. Since ignorance is not a sin (John 9:41) and since Jesus is compassionate (Matt 9:36), we should be very cautious about claiming that someone who believes such-and-such cannot be saved or that someone must believe this and that to be saved.