He wasn't wrong.....and he is not God. (Matthew 24:36) Those renderings show that human translators didn't have a clue what he was talking about.
The first rendering is a pathetic translation of the original.
According to Strongs, the word "
generation" used in that verse "
genea" can mean......
- the several ranks of natural descent, the successive members of a genealogy
- metaph. a group of men very like each other in endowments, pursuits, character"
But this is hardly acknowledged by many translators, so they render Jesus' words as nonsensical.
Since Jesus was talking about his return in the future, these events described in Matthew 24 would allow his disciples at that time to comprehend the "signs" indicating that Christ was now ruling in heaven. These were the signs of his "presence" (parousia) not of his "manifestation" to judge the world. (These are two separate events)
Jesus would direct a monumental preaching campaign in "all the inhabited earth as a witness to all the nations" that these were the "last days" before God's Kingdom rule directly intervenes in man's affairs to clean up the rot. (Matthew 24:14; Daniel 2:44) After this witness is given to God's satisfaction, then Jesus will manifest himself to judge the nations....the "end" of this wicked world of mankind will then come.
The ones he was talking to initially were those assigned to rule with him in heaven, (all of the first Christians were of that group) but there was a problem in choosing these ones once the foretold apostasy set in. They became almost lost in the world of "weeds" (counterfeit Christianity) sown by the devil. It would not be until the "time of the end" began that God would again cleanse his worshippers, and choose the remaining ones of that "generation". This fits the second definition mentioned above.