Oh, no. I can't believe you said that.
The way we understand Scripture is to interpret one passage by another passage. If Jesus uses the phrase "this generation" throughout the gospels to consistently speak of the generation of Jews living in that day, then it would be quite arbitray to change meanings elsewhere without good reason.
Of course if you are creating a futurist eschatology out of whole clothe, then any reason is a good reason I guess.
"For as Jonah became a sign to the Ninevites, so also the Son of Man will be to this generation." (Luke 11:31)
FIRST, you use the immediate context of the same author to interpret the author.
There is another use of the same formula in that same context. The very same DISCOURSE, as a matter of fact.
Once again you are comparing two events that have different outcomes. When Jonah announced the destruction of Ninevah, they believed him and they were not destroyed. How does that prefigure the destruction of Jerusalem?