"And when He was demanded of the Pharisees, when the kingdom of God should come, He answered them and said, The kingdom of God cometh not with observation: Neither shall they say, Lo here! or lo there! for, behold, the kingdom of God is within you." Luke 17:20-21
Don't be confused by the rhetoric of the unbelieving world. The kingdom that is to come, after the rapture and after the millennial reign of Christ is the outward expression of an already existing work. The kingdom that is within is found in the person of Jesus Christ that has come to dwell in us in the person of the Holy Spirit. The reason the Pharisees and those today that are not believers were looking for a kingdom to come was that they did/do not possess the kingdom within.
Only those who possess the kingdom within will participate in the kingdom to come. The kingdom to come is the presence of those who possess the kingdom within. The reason there is so much disagreement about this subject is that those who do not possess the kingdom within, in some cases, are teaching those who do, that they don't. The Bible told us that in these days that we are in that the wheat would be mixed with the chaff and that there would be infiltrators inside the church.
These infiltrators are not necessarily unbelievers, but in many cases, they are ignorant of the Word of God. In some cases they have been taught things that are extra-biblical that they never questioned the teaching of and searched out the Word to find the truth and now they are purporting the same rhetoric, as if it were the Word of God. That's how these silly doctrines of men get started. Of course, once you take a stand on something, it's hard to condescend if new light is shown and you see the truth. Our ego and pride keep us from ever really reaching the pinnacle of our true position with Christ.
That's why it is so important to read the Word of God for yourself. Jesus taught a clear and concise truth, because He is the truth. "The kingdom of God is within you."