When speaking of Jesus' second coming what does Paul mean by the word "shortly" in Romans 16:20 or the author of Revelation 22:10, 12, 20 by "the time is near" and "I am coming quickly"?
To understand what is meant let us look at Hebrews 10:37: "For yet a little while, and he that shall come will come, and will not tarry." This verse is derived in part from the Septuagint's rendering of Habbakuk 2:3.
The early Christian church was a community living in daily expectation of the return of Jesus. The author of the Book of Hebrews expressed his agreement with this expectation. In Hebrews 10:37 he is solely concerned with the immediate future and his expectation that Jesus will return shortly: "For yet a little while and he that shall come will come, and will not tarry." In this verse the author of Hebrews teaches, in accordance with the other New Testament authors, that Jesus would be returning in what was then the near future as time is reckoned in human terms. He utilizes some of Habbakuk's wording to convey his own message. In the Book of Habbakuk, God informs the prophet that even when the wicked temporarily flourish one should be patient and wait, for faith in God will be vindicated. God promises that the vindication will come in its appointed time, not before, nor after. It is to come in God's own time. This fits well into the scheme of history addressed by the psalmist's words that "a thousand years in Your sight are but as yesterday when it is passed, and as a watch in the night" (Psalm 90:4). For his part, however, the author of Hebrews indicates in his choice of the words "for yet a little while" a specific time period in which to expect the arrival of the second coming.
The expectation of Paul and the other New Testament authors was for the speedy arrival of the second coming in their generation. The use of "for yet a little while," "shortly," "the time is near," and "I am coming quickly" point to the utter failure of the predictions that Jesus was coming a second time to do what he did not accomplish the first time.