Here is the very latest writes about "This Generation." Looks like they are preparing to change it again -- now the focus is on 70 C.E., instead of modern times:
Jesus--The Way book (2015), Page 254 and Pages 258-259:
He warns: “Truly I say to you, all these things will come upon this generation.” (Matthew 23:34-36) That proves to be the case in 70 C.E. when the Roman armies destroy Jerusalem and many thousands of Jews perish. ...
How, though, would Jesus’ disciples who are living during this foretold period be able to determine the nearness of the end? Jesus gives an illustration about a fig tree: “Just as soon as its young branch grows tender and sprouts its leaves, you know that summer is near. Likewise also you, when you see all these things, know that he is near at the doors. Truly I say to you that this generation will by no means pass away until all these things happen.”—Matthew 24:32-34.
Thus, when his disciples see the many different features of the sign being fulfilled, they should realize that the end is near.
-----
Insight Book (2015 Edition), Volume 1, Page 918:
“This Generation” of Christ’s Prophecies.
When Bible prophecy speaks of “this generation,” it is necessary to consider the context to determine what generation is meant. Jesus Christ, when denouncing the Jewish religious leaders, concluded by saying: “Truly I say to you, All these things will come upon this generation.” History recounts that about 37 years later (in 70 C.E.) that contemporary generation personally experienced the destruction of Jerusalem, as foretold.—Mt 23:36.
Later that same day, Jesus again used practically the same words, saying: “Truly I say to you that this generation will by no means pass away until all these things occur.” (Mt 24:34) In this instance, Jesus was answering a question regarding the desolation of Jerusalem and its temple as well as regarding the sign of his presence and of the conclusion of the system of things. So his comment about “this generation” logically had an application down to 70 C.E. However, he was also using the word “generation” with reference to humans whose lives would in some way be associated with the foretold events during his presence.—Mt 24.