ANSWER: Oh, heavens no! Their view will not fly in any form or fashion! The messianic kingdom will be actual, historic, and a specific event that unfolds in time. To fully understand Luke 17:21 you must tie it together with 10:9, 11. In my Luke commentary on 17:21 I write: "in every reference to the arrival, or the coming of the kingdom in the Gospels, the verb is in the Perfect Tense. In Luke the NASB translates 10:9, 11 correctly: 'The kingdom of God has come near you." It has come up to the present, up to the moment, but it has not been inaugurated. 'It has been on its way, and it has arrived, but it has in no way begun!'" "Has come" is egiken in Greek and is from the verb engizo. It is a Perfect Active Indicative and this verb form is used almost always to convey the idea that the kingdom is presented but not inaugurated or fulfilled. That is, the "coming" of the kingdom has reached a finished state. If the Jews had repented as a nation, in theory, the kingdom would have started. Of course the God in His Prescience knew they would reject it! "It has finished coming" but is not necessarily now in operation. There is a cogent reason that the Perfect Tense is used so consistently when discussing the kingdom arrival. Dana & Mantey, the great Greek grammarians, write: "It is best to assume that there is a reason for the Perfect [Tense] wherever it occurs."
In the Greek text of 10:9, near is the Preposition epi with the root idea here of upon. The point is that the kingdom has made its arrival because the King is present, but this does not mean that the kingdom has started. "The kingdom of God is resting over you Pharisees but has not begun!" It is impossible that the idea of 17:21 would be that the kingdom is now operating within believers. Christ is talking with the Pharisees who, for the most part, were not true believers!
The BKC says:
Some feel that the force of the expression is "within your possession or within your reach," Jesus' point was that He was standing right in their midst. All they had to do was acknowledge that He is indeed the Messiah who could bring in the kingdom—and then the kingdom would come.
In the book The End Times Controversy (eds. Tim LaHaye & Tommy Ice) I wrote:
Based on the grammar and context of a given passage, engus may simply mean that something is coming near, approaching, or being brought near. But does this guarantee that the referred-to event will take place immediately? If John the Baptist and Christ said the "kingdom of heaven is at hand" (Matthew 3:2; 17; 10:7), is it inherent in the verb that the kingdom will come right then? Could the kingdom be near or certain but not actually arrive because of some other factors? As well, could the verb tens simply be telling us that that the kingdom is certainly on its way? Could it be that the Jewish rabbis understood that the kingdom would not be announced yet, not arrive because the nation of Israel was unworthy — that it was not inaugurated because of the sins of the nation? Can it be shown by the writings of the church fathers that they understood this problem? The church fathers indicate that the kingdom was yet to arrive—perhaps in their day, or beyond.
Thanks for asking.
Dr. Mal Couch