Well to the above posts it really depends what you mean by belief in the Son and what it looks like to follow the way of Jesus. Does belief mean you must know that there was a Jewish man (who was God incarnate) who lived 2000 years ago who died on a tree to save you from your sin? Or less specific, for example, that God incarnate died to save you. Or simply faith and an attitude of love towards a 'higher being'?
I'll give my view now;
Consider this, was Abraham a jew or under God's promise when he was born? I would say no since it all began with Abraham (as Paul says Abraham was saved by his faith). That would mean Abraham was a man like anyone but who has great faith in God and is therefore saved. Would it not be possible then that other people at the time of Abraham could also be saved by faith?
If that is true then it seems likely that when the Hebrews became God's chosen people God would not in effect make unsaveable most people on earth because of Abrahams extreme faith because they happened to be born to the wrong people group.
If then salvation was possible for all people with faith before Christ why would Christ's death then condemn most people? For Christ did not come to condemn the world butto save it. Christ death and resurrection is ment to be good news to all people so it seems highly unloving for the possibility of salvation to be removed from most people because Christ died for them.
Would it not seem then that all people can be saved by faith and an attitude of love directed towards their understanding of God as best as possible.
Of course those who are Christians have a very special relationship with God like no other religion and the fullness of grace can only be felt in Christianity and only Christians can be sure of their salvation.
Of course Im not saying this is most definitely true, but it is a theory.
Solarwave