I guess I'm going to have to disagree. I don't think that the Kansas City Missouri LDS (Mormon) Temple fulfilled this prophecy.
Let's look closer at verse four:
4 Verily this is the word of the Lord, that the city New Jerusalem shall be built by the gathering of the saints, beginning at this place, even the place of the temple, which temple shall be reared in this generation.
It says that the city of New Jerusalem shall be built by the gathering of the saints.
It then goes on to say where the beginning of the gathering of the saints would take place. Where is that place? It is "this place." It is clearly a localized reference to whatever place Joseph was at when this revelation was given. Where was this revelation given? It was given in Kirtland, Ohio.
It seems to me that "this place, even the place of the temple" is referring to the temple lot in Kirtland Ohio, not the temple lot in Jackson County.
This verse then goes on to prophecy that, the temple which will be built upon the "this place", "shall be reared in this generation." The Kirtland temple was reared in the generation of those people.
I think it is so sad that people look at this prophecy as failed because the New Jerusalem temple wasn't finished in the generation of those people.
The reason I like my understanding of this is because it doesn't require any shoehorning of modern temples(no offense) nor redefining of the word "generation"(again no offense). It just requires us to use a little grammar and geography.
I'm afraid that last paragraph may have sounded like I was talking down to others. That wasn't my intention.