"Jesus was referring to the generation that was to "see all these things", not the generation of his day. (Matthew 24:33) Likewise also you, when you see all these things, know that he is near at the doors."
Well Mr G, it doesn't say that nor can it be inferred from what is said or the context.
Nor would it make any sense to say something like "the generation that sees those trees over yonder will not pass away until they see those trees". That is self evident and it is pointless to say a future event will be seen by those seeing it. It would make even less sense to emphasise such a statement with "verily I say to you".
The specific use of "this generation" clearly refers to "this generation" not some future generation.
Not to mention that other accounts refer to "some standing here" etc.
More likely, the prophesy is either just plain wrong or was not meant to be taken literally or is a mixture of different accounts by Jesus about separate events and experiences which the Gospel writers mish mashed together into a "return of the King story" to fulfil OT prophesies and give hope to persecuted fellow early Christians.
If that was the purpose it has been very successful, lasting 2,000 yrs and counting.
