On the last day of the feast of tabernacles long ago, Jesus said this:
John 7:37 In the last day, that great day of the feast, Jesus stood and cried, saying, If any man thirst, let him come unto me, and drink. 38 He that believeth on me, as the scripture hath said, out of his belly shall flow rivers of living water. 39 (But this spake he of the Spirit, which they that believe on him should receive: for the Holy Ghost was not yet given; because that Jesus was not yet glorified.)
This is what Zechariah 14:8 is about. You need to learn to use the NT to shine light on the OT prophecies for you. You also should be careful about interpreting things too literally. The entire book of Zechariah is a mix of literal and symbolic text, so you should not assume that it's all literal.
Already true.
Matthew 28:16 Then the eleven disciples went away into Galilee, into a mountain where Jesus had appointed them. 17 And when they saw him, they worshipped him: but some doubted. 18 And Jesus came and spake unto them, saying, All power is given unto me in heaven and in earth.
Revelation 1:5 and from Jesus Christ, who IS the faithful witness, the firstborn from the dead, and the ruler of the kings of the earth. To him who loves us and has freed us from our sins by his blood, 6 and has made us to be a kingdom and priests to serve his God and Father—to him be glory and power for ever and ever! Amen.
There are a couple major problems with seeing a future fulfillment of what is described here.
First, it's talking about being required to go up to Jerusalem to worship God.
That contradicts this:
John 4:19 “Sir,” the woman said, “I can see that you are a prophet. 20 Our ancestors worshiped on this mountain, but you Jews claim that the place where we must worship is in Jerusalem.” 21 “Woman,” Jesus replied, “believe me, a time is coming when you will worship the Father neither on this mountain nor in Jerusalem. 22 You Samaritans worship what you do not know; we worship what we do know, for salvation is from the Jews. Yet a time is coming and has now come when the true worshipers will worship the Father in the Spirit and in truth, for they are the kind of worshipers the Father seeks. 24 God is spirit, and his worshipers must worship in the Spirit and in truth.”
To think that what Jesus said here will one day no longer be true makes no sense. It will always be true from now into eternity.
Another problem with seeing this as having a future fulfillment is the mention of the requirement to keep the feast of tabernacles and the reference to the "pots" and such. Taken literally and as referring to the future, that would mean animal sacrifices and offerings would be reinstated because animal sacrifices and offerings were required during the keeping of the feast of tabernacles.
But, that would contradict this:
Hebrews 10:1 For the law having a shadow of good things to come, and not the very image of the things, can never with those sacrifices which they offered year by year continually make the comers thereunto perfect. 2 For then would they not have ceased to be offered? because that the worshippers once purged should have had no more conscience of sins. 3 But in those sacrifices there is a remembrance again made of sins every year. 4 For it is not possible that the blood of bulls and of goats should take away sins. 5 Wherefore when he cometh into the world, he saith, Sacrifice and offering thou wouldest not, but a body hast thou prepared me: 6 In burnt offerings and sacrifices for sin thou hast had no pleasure. 7 Then said I, Lo, I come (in the volume of the book it is written of me,) to do thy will, O God. 8 Above when he said, Sacrifice and offering and burnt offerings and offering for sin thou wouldest not, neither hadst pleasure therein; which are offered by the law; 9 Then said he, Lo, I come to do thy will, O God. He taketh away the first, that he may establish the second. 10 By the which will we are sanctified through the offering of the body of Jesus Christ once for all.
This passage indicates that the old covenant animal sacrifices performed as a requirement of the law of Moses would result in "a remembrance again made of sins every year". Those sacrifices, of course, could not take away sins. God no longer wanted those sacrifices and took no pleasure in them. So, He sent His Son Jesus who came and sacrificed Himself to take away the first (old covenant) in order to "establish the second" (new covenant). And He did that "once for all". Clearly, there would never be any need or desire for animal sacrifices again because of Christ's "once for all" sacrifice. So, to think that animal sacrifices would be reinstated again in the future contradicts scripture like this and would be a huge insult to what Christ accomplished on the cross when He did away with the old covenant animal sacrifices.