Jehovah's Witnesses have to put on blinders when it comes to this and like sections of Scripture. But Christianity is general doesn't suggest much better.
To illustrate, in the NABRE, the official Catholic Bible of the United States of America, the footnote to this parable reads:
Because of that heavy allegorizing, some scholars think that it does not in any way go back to Jesus, but represents the theology of the later church. That judgment applies to the Marcan parallel as well, although the allegorizing has gone farther in Matthew. There are others who believe that while many of the allegorical elements are due to church sources, they have been added to a basic parable spoken by Jesus. This view is now supported by the Gospel of Thomas 65, where a less allegorized and probably more primitive form of the parable is found.
This, mind you, is from the Roman Catholic Church, the denomination that makes claim to writing and officially selecting and canonizing the Gospel of Matthew. (If one counts this this happened when the Catholic Church was united with the Orthodox Church before the schism, this claim is not without some historical merit.) In other words, contrary to JW teaching (and due to critical analysis of manuscript transmission), this was not a "prediction" of Jesus or even uttered by him.
After the death of Jesus, his followers had to develop a way of making his crucifixion appear as if it were "part of the plan" from the beginning. In this instance a parable of Jesus appears to have been extended and such liberties taken with it that it now reads in such a manner to teach that the upcoming Passion events of Jesus never caught Jesus off guard (and thus shouldn't shake his followers who may be stumbled by the idea of a suffering and dying messiah).
It needs to be emphasized that Catholics see this type of interpolation as part of the "inspiration process." Jesus never really spoke this parable exactly, but by virtue of the fact that his followers wrote this and the Church canonized it emphasizes their conviction that this "added" meaning was written under the direction of the Holy Spirit. This is how John 16:13-14 is interpreted in reference to this, not that the Spirit would introduce further teachings but would interpret what had occurred and been said by Jesus in a new light.