There is a whole little section of the Greek that does not appear in the KJV though it does appear in at least one more modern translation (NASB). Again, as we saw in Luke 22:16 and in the similar verse in Matthew 26:29, the verbs here are not  the future tense. They are verbs of possibility. This verse is very different that the version in Matthew. While some of the difference are stylistic (Luke commonly offers "kingdom of God" instead of the other descriptions of the kingdom used in Matthew), the big question with such verses is did he say both things or are both just potentially faulty memories of what he said? I tend to go with the "both" theory since Jesus seems to be a pretty verbose person who said more than people could get written down.

The word translated as "for" introduces a reason or explanation so "because" and, in questions, "why."

The word translated as "I say" is the most common word that means "to say," and "to speak," but it also means "to teach," which seems to be the way Christ uses it more frequently. Christ usually uses this word to refer to his own speaking or teaching.

The Greek pronoun "unto you" here is plural and in the form of an indirect object, "to you", "for you", etc. 

The word "I will...drink" is the Greek for meaning to "drink". It also has a double meaning. "To drink" also means "to celebrate." The form of this verb is not the future tense, but a form, which when used with this form of negative is used either to make this future seem doubtful or certain, "it may be that" or "it is certain". We see this same form in Luke 22:16 and Matthew 26:29.

The "not" here is both of the Greek negatives used together. Greek has two negatives, one objective, one subjective. The use of both together is more extreme, like saying "never ever".

There is a phrase here that means "from the present" or, as we would say, "from now on". The word that should be translated as "from" means "from" in both location and when referring to a source. The "now on" is literally "the now", which means "the present". The word that should be translated as "this" is the Greek definite article, which usually precedes a noun and, without a noun, takes the meaning of "the one." The Greek article is much closer to our demonstrative pronouns ("this", "that", "these", "those"). See this article for more.     The Greek word that should be translated as "now" \means "now", "at the present moment","presently," and "as it is."

The word translated as "of" means "from" in both location and when referring to a source. It is the same word as used in the phrase above repeated here.

The term used for "fruit" here means both "offspring" and "product." It is not the Greek word usually translated as "fruit". Except for the similar verse in Matthew 26:29, this word has only been used previously translated in the Gospel as "generation" in the phrase "generation of vipers," (Matthew 12:34, Matthew 23:33 but originally used by John the Baptist in Matthew 3:7) referring specifically, the Pharisees and perhaps meaning the "product of vipers," that is, poison." It is NOT the term Christ commonly uses to refer to "fruit" as in "judging a tree by its fruit."

The terms translated as "of the vine" is means "vine" and specifically "grape vine". Christ has used the related term, vineyard, many time but this word is less common.

"Until" is from the conjunction that  means "until", "till," and "in order that" and "up to the point that."

There is another untranslated word here. It is a demonstrative pronoun ("this" "that"), but it often acts as a pronoun ("the one that), especially a connective pronoun ("the one that") introducing a dependent clause.  Here, it introduces the following short sentence.

The word translated as "kingdom" can be the region, the reign, the castle or the authority of a ruler. Christ does not seem to use it to mean a physical region, so its translation as "reign" or "realm" seems more appropriate. This is especially true because the "reign" of a king means the execution of his will.

The word translated as "of God" means "God" and "deity." It is introduced with an article, so "the God." Jesus often uses it this way perhaps to indicate the one God as opposed to the pagan gods.

The word translated as "shall come" primarily means "to start out" but Christ usually uses it to mean "come" but not always. It indicates movement, especially its beginning, without indicating a direction toward or away from anything, so it works either as "come" or "go," but it is more like our phrase "being underway." Our English word "show up" captures both the "start" and "come" ideas.   The form is not the future tense, as translated. It is again in the form of a possibility "might show up".