It seems to me that, in the context of that speech, he is anticipating a simlar kind of "purging" as happened in the overthrow of the other regimes he points at, one of which happened by internal collapse, one by popular revolution, and one by a convenient American invasion which eliminated a powerful enemy of Iran without a need to lift a finger.

It does sound to me more like a politician whistling in the wind, and talking up the possibility of a future intifada rather than revealing plans for making war, let alone the suicidal nuclear attack which it has been widely interpreted as meaning.

"Very soon" can mean anything. In the context where the Crusader Kingdoms are seen as a precedent for Israel, "very soon" could mean a century or two.

I'm rather reminded of the way Kruschev's words translated as "We will bury you" were widely interpreted as a prophecy of war. In fact the words were more accurately translated as "we will attend your funeral", and were essentially about competition between economic systems - the competition which in the end did end in the "funeral" of one of the systems, just not the one Kruschev had predicted.