This prophecy speaks of a massive soul harvest that will be a bookend to the church period and bring it to a close.  This isn't the gigantic soul harvest spoken of to occur during the Tribulation, but rather a global revival and soul harvest prior to that time, which will bring in the final saints of the church period, and bring this time period, and biblical dispensation, to a close, which will then followed by the Tribulation and the Millennial Kingdom.  As a special bit of note, if I'm understanding this correctly, and its related supporting bible verses, this will occur side by side with the wheat and tares prophecy of Matthew.