Luke 21:34 And take heed to yourselves, lest at any time your hearts be overcharged with surfeiting, and drunkenness, and cares of this life, and so that day come upon you unawares.Whatever "the hour of temptation, which shall come upon all the world" is referring to, it's something that at least could have potentially occurred during the lifetimes of those in that first century church. If it's referring to the great tribulation before Christ's return, then remember that no one knows when that will happen except for the Father (Matthew 24:36). So, if that's what Jesus was referring to, then He would only have been talking about it in terms of what He would do for them if the hour of temptation came upon the world while they were still alive. And He wouldn't have known if they would be or not since He didn't know when He would return and only the Father knew that (see Matthew 24:36).
35 For as a snare shall it come on all them that dwell on the face of the whole earth.
36 Watch ye therefore, and pray always, that ye may be accounted worthy to escape all these things that shall come to pass, and to stand before the Son of man.