The words of the prophecy in question are:
"Seventy weeks are determined upon thy people and upon thy holy city, to finish the transgression, and to make an end of sins, and to make reconciliation for iniquity, and to bring in everlasting righteousness, and to seal up the vision and prophecy, and to anoint the most Holy." (Daniel 9:24)
First, we need to understand that, although most of our English translations say seventy weeks, the Hebrew word translated weeks was shabuwa' (word number 7620 in Strongs Hebrew Dictionary) This word was used in the Old Testament for both a period of seven days and a period of seven years. Only the context could show whether days of years was meant. An in this case, the context clearly shows that the meaning could not even possibly been days. So it is not simply interpretation to take seventy weeks as meaning 490 years. This is a fully legitimate meaning of the Hebrew words used here.
Daniel was told, "Know therefore and understand, that from the going forth of the commandment to restore and to build Jerusalem unto the Messiah the Prince shall be seven weeks, and threescore and two weeks: the street shall be built again, and the wall, even in troublous times." (Daniel 9:26) Here we have sixty-nine weeks, or 483 years, from the going forth of the commandment to Messiah the Prince.
But now the Divinely inspired account contains a break. We read, "And after threescore and two weeks shall Messiah be cut off, but not for himself: and the people of the prince that shall come shall destroy the city and the sanctuary; and the end thereof shall be with a flood, and unto the end of the war desolations are determined." (Daniel 9:25-26)
Two things were to happen after the sixty-two week second part of this account. And we know that both of them indeed happened exactly as explicitly stated. Messiah would be cut off, and the people of the prince that shall come shall destroy the city and the sanctuary. Messiah was indeed cut off, and the city and the sanctuary were indeed destroyed. We know from history that these two events did not happen within a seven year period. Most historians feel that our calendar is in error, and the actual date of Jesus birth was 4 BC. Since Jesus lived thirty-three years, that puts his death in 29 A.D. But the city was not destroyed until 70 A.D., forty-one years after that. So even if there are small errors in the accepted dates of history, we absolutely know that the city and the sanctuary were not destroyed in the same week (seven year period) that our Lord was crucified. But we need to notice that both of these events are presented before the last week is even mentioned. So here we see an absolutely undeniable break in the scriptural account of the seventy weeks.
But the last week is treated differently. It does not even say that this is the seventieth week. The only reason we know that it is the seventieth week is because all the rest of the weeks had already been used up. So this week had to be the seventieth one. We read, "And he shall confirm the covenant with many for one week: and in the midst of the week he shall cause the sacrifice and the oblation to cease, and for the overspreading of abominations he shall make it desolate, even until the consummation, and that determined shall be poured upon the desolate." (Daniel 9:27)
Now many imagine that this verse speaks of the cross. They want to interpret the word for in this verse as in, and claim that this was speaking of Jesus confirming Gods covenant with us in the seventieth week, and claim that Jesus was crucified at the middle of the seventieth week. But even if history were wrong by so many years, this interpretation does violence to the structure of the prophecy. For the last week is not even mentioned until after the two events that were to take place after the sixty-ninth week.
But an end time covenant that will not be fulfilled is clearly mentioned in other Old Testament prophecies. One of these is Isaiah 28:14-18, where we read, Wherefore hear the word of the LORD, ye scornful men, that rule this people which is in Jerusalem. Because ye have said, We have made a covenant with death, and with hell are we at agreement; when the overflowing scourge shall pass through, it shall not come unto us: for we have made lies our refuge, and under falsehood have we hid ourselves: Therefore thus saith the Lord GOD, Behold, I lay in Zion for a foundation a stone, a tried stone, a precious corner stone, a sure foundation: he that believeth shall not make haste. Judgment also will I lay to the line, and righteousness to the plummet: and the hail shall sweep away the refuge of lies, and the waters shall overflow the hiding place. And your covenant with death shall be disannulled, and your agreement with hell shall not stand; when the overflowing scourge shall pass through, then ye shall be trodden down by it.
Again, in Isaiah 57:7-9 we read, Upon a lofty and high mountain hast thou set thy bed: even thither wentest thou up to offer sacrifice. Behind the doors also and the posts hast thou set up thy remembrance: for thou hast discovered thyself to another than me, and art gone up; thou hast enlarged thy bed, and made thee a covenant with them; thou lovedst their bed where thou sawest it. And thou wentest to the king with ointment, and didst increase thy perfumes, and didst send thy messengers far off, and didst debase thyself even unto hell.
So we see that the scriptures indeed clearly foretell a future covenant that God will not allow to be fulfilled. Daniel 9:27 is only one of several places where this covenant in mentioned.