Jesus appeared to be making the point that someone in heaven is greater than someone still on earth. No matter how great and faithful John was at this mention of him, he was still a human and still alive. A lesser one in heaven, Jesus argued, would naturally be greater than John is (at that moment) since John was still a living human.
Len Miller.
The expression Kingdom of the Heavens is not talking about someone in heaven. It is the Jewish way of saying Kingdom of God. The terms are interchangeable. Read the verse in Luke. Lu 7:28 For I say unto you, Among those that are born of women there is not a greater prophet than John the Baptist: but he that is least in the kingdom of God is greater than he. Luke wrote for a Greek audience and so used the alternate rendering for this Kingdom. The Gospels do not always quote our Lord precisely but are mindful of the intended audience and we should be aware of this. So what is this all about? Will such a person in this Kingdom go to a place unknown to us called heaven? No! This Kingdom of Heaven (or God) will be right here on earth as promised. Entry is possible only be being selected for this Kingdom either by being resurrected of changed. Furthermore despite John's greatness, he was still mortal. Anyone that that gains entry into this promised Kingdom will be an immortal. But there is something else more important. The NIV renders this more clearly like this: 12 From the days of John the Baptist until now, the kingdom of heaven has been forcefully advancing, and forceful men lay hold of it. 13 For all the Prophets and the Law prophesied until John. So what does this mean? Up until now the Law provided the vehicle for salvation or entry pointing to such a Kingdom to come. But now since John we have an opportunity to become a part of its administration (Kingdom) and not just a great crowd associated with it's Paradise. Our Lord is not excluding John from being a part of its administration. After all John was there alive and in time for such an administration. In fact forceful men like John would lay hold of it just as our Lord promised. But that would be then in this projected Kingdom since any such administrator at that time would be greater than this very great prophet John was now.
Joseph