Jesus rated John the Baptist as the greatest “among those born of women” (Luke 7:28) hence after his death he should naturally go to heaven—especially so lesser ones like Enoch, Abraham are already in the Kingdom of Heaven. (Hebrews 11: 5, 6; 13-16)
In view of the direct statement of Jesus: “I say to you that many will come from the east and the west to share the banquet with Abraham, Isaac, and Jacob in the kingdom of heaven” (Mathew 8:11), people like Abraham are definitely in heaven. Hence it is obvious that ‘the one who is least in the kingdom of God is greater than John’ must be a later adoption to project Jesus as the first-fruit (which is again meaningless as Jesus was already from heaven, and was only to return to heaven)
The verse in Luke 7:28: “I tell you, among those born of women there is no one greater than John; yet the one who is least in the kingdom of God is greater than he” is like Nobel Prize committee saying: “We tell you, among all those living on earth there is no one who has contributed to world-peace as much like Juan Manuel Santos; yet there is no Nobel Prize for Peace for him this year or in any years to come.” Latter part of the sentence makes no sense.
Interestingly, the writer of Hebrews had a clear understanding of life and what happens after life. For him it was like children coming out from their house on to play-ground, and returning to house from where they came. (Hebrew 11:13-16) Such a simple view of life was clouded by complicated teaching of grace or undeserved kindness through faith in the sacrificial death of Jesus (which is again meaningless as it is linked to some ancient myth borrowed from other cultures).