The scriptures often speak of future events using a verb in the present tense in order to indicate their ultimate certainty in the plans of God.

For example, in Matt. 26:2 Jesus said "after two days the Passover comes, and the Son of Man is delivered up to be crucified";
In the parables the preaching of the kingdom is represented as a growing, spreading mustard seed (Mat 13.31-32);
Jesus describes his followers as the people of the kingdom (Mat 13.38);
These kingdom people are being collected by a net that is being cast (Mat 13.47).
And Jesus describes the Kingdom as a hidden treasure that is found by would be kingdom people (Matt. 13:44-45);

The saying “the Kingdom is here or there" is explained by the following verses describing the future arrival of the Son of Man.
v 22 “The time is coming when you will long to see one of the days of the Son of Man, but you will not see it."
v 23 People will tell you, ‘There he is!’ or ‘Here he is!’ Do not go running off after them. 
v 24 For the Son of Man in his day will be like the lightning, which flashes and lights up the sky from one end to the other. 
v 26 “Just as it was in the days of Noah, so also will it be in the days of the Son of Man." 
v 30 “It will be just like this on the day the Son of Man is revealed." 

jesuskingdomgospel.com