On this side of the cross one could argue about aborted babies, people without mental faculties, etc. Are the "Christian" in the strict term? Will they go to heaven? At one time Christians were termed "the Way". The term Christian was applied later. They also are not "Christians" in the strong sense of the word.
So you can see that your question is murky. Personally, I categorized people into believers and non-believers. The scriptures calls them the righteous and unrighteous, the saints and the sinners, those who have received mercy and those destined for wrath, children of light and children of darkness, etc. But all believers share one thing in common, they recognize their sinfulness before God and a need for God to redeem them. The only religion today that offers this hope is Christianity through Jesus our Lord. And, I might add, many "Christian" churches today don't even do this and there are no other religions that offer this promise. There is salvation in no one else.
Fair and intellectually honest reply...thank you