Not clear as a bell at all. In fact, Alfred Edersheim, a Jewish convert to Christ and well-familiar with biblical imagery, wrote this about Matthew 24:
From the fig tree, under which on that spring afternoon they may have rested, they were to learn a parable. We can picture Christ taking one of its twigs, just as its softening tips were bursting into young leaf. Surely this meant that summer was nigh--not that it had actually come. The distinction is important; for it seems to prove that 'all these things' which were to indicate to them that 'it' was 'near, even at the doors,' and which were to be fulfilled ere 'this generation' had passed away, could not have referred to the last signs connected with the advent of Christ, but must apply to the previous prediction of the destruction of Jerusalem and of the Jewish commonwealth. This too is a very simple and satisfactory explanation of the words, This generation shall not pass till all these things be fulfilled. If those words be taken as His answer to the question, When shall these things be? (v. 3), they are easy of interpretation; but if their application be postponed to the far off future they present much difficulty. For example, thus to postpone their application would make the Lord contradict His positive and most emphatic statement that no signs would precede and give warning of His second advent. (Life and Times of Jesus the Messiah, Chapter VI)It was clear to Edersheim that "this generation" must refer to the 1st century generation of Jews to whom Jesus was speaking.
You are ignoring Luke 21. All is clarified in Luke. Luke absolutely uses "this" in a future present sense just a few sentences earlier.
It's not the least bit of a problem to realize that Edersheim is merely thoroughly wrong--regardless of his Jewishness, his scholarship, biases, whatever--he's simply thoroughly wrong.