TD:
I hate to be the fly in the punch bowl here (Because I think 607 BC is hogwash) but Luke 21:24 is actually a text book example of what is called the periphrastic progressive. (Present participle + Future form of to be)
The conclusion that this verse indicates a present continuing action (a misrepresentation of Ernest De Witt Burton, whom the site you provided copied verbatim) seems to have fairly limited support, and seems more like it is being shoehorned into that grammatical construction to suit preconceived doctrines. In fact, searching Google for "periphrastic progressive "luke 21:24" -burton" (i.e. excluding "Burton") only returns eight results, some of which are still in reference to Burton (such as the one at www.dabar.org/burtonmoodstenses/08-future_ind.htm, which also quotes Burton verbatim), and some are on JW forum discussions about the verse.
In fact, the interpolated "[continue to]" isn't even directly relevant to the grammatical form discussed. Burton states that "The force is that of a Progressive Future", indicating that something will happen in the future and it will then keep happening. This is very clearly shown by the other example Burton provides:
- Luke 5:10; ἀνθρώπους ἔσῃ ζωγρῶν, thou shalt catch men, i.e. shalt be a catcher of men.
James and John were not already 'catching men'. It was a future action that would then continue. It therefore appears that it isn't even Burton's intent to say that this grammatical form is the reason for the insertion of 'continue to', and that it is only there because of an incidental interpretation that the Jews already being under Roman rule was the same as the 'trampling'.