Wait, you mean from Daniel 9?
Let's quote that here for the sake of clarity; Daniël receives a prophesy from the angel Gabriel:
[quote author=Daniel 9:24-27]Seventy weeks are decreed for your people and your holy city: to finish the transgression, to put an end to sin, and to atone for iniquity, to bring in everlasting righteousness, to seal both vision and prophet, and to anoint a most holy place.
Know therefore and understand: from the time that the word went out to restore and rebuild Jerusalem until the time of an anointed prince, there shall be seven weeks; and for sixty-two weeks it shall be built again with streets and moat, but in a troubled time.
After the sixty-two weeks, an anointed one shall be cut off and shall have nothing, and the troops of the prince who is to come shall destroy the city and the sanctuary. Its end shall come with a flood, and to the end there shall be war. Desolations are decreed.
He shall make a strong covenant with many for one week, and for half of the week he shall make sacrifice and offering cease; and in their place shall be an abomination that desolates, until the decreed end is poured out upon the desolator.[/quote]
Apparently, the word "week" in Hebrew also means "seven", so it should read "Seventy sevens", which is usually interpreted as 70 sevens of years. This is because the events/phases described in the prophesy roughly correspond with the biblical history of Israel, if one takes the restoration of Jerusalem and the Temple as being Xerxes' degree to Ezra in (about) 458 BC to restore Jeruzalem's walls, and counts the years as 360-day "Prophetic years".
In verse 26, we count
after the first 69 "weeks of years", "an anointed one shall be cut off and shall have nothing"; this is usually interpreted by Christians to be Jesus, who is annointed because he's the Messiah, and who is killed and abandoned. The destruction of the city and sanctuary that follow are usually interpreted to be the destruction of Jeruzalem and the Temple, of course (although the interpretations of who the "prince to come" is differ wildly).
After this we get the first reference to the Abomination in the Old Testament, who is to do bad things for half a "week"; this actually corresponds nicely with Daniel 12:
[quote author=Daniel 12:11]And from the time that the daily sacrifice shall be taken away, and the abomination that maketh desolate set up, there shall be a thousand two hundred and ninety days.[/quote]
...which is roughly 3 and a half year, so half a "week".
In your interpretation, the 70 "weeks of years" are a continuous sequence of phases, which makes sense of course. But if you read closely, you see that verse 26 is placed after the first 79 "weeks", and the events of the last "week" (verse 27) take place after that. Hence, there is a "gap" in the chronology, which apparently is placed by some scholars in the middle of the 70th "week" rather than between the 69th and 70th (with Jesus rather than the Antichrist ceasing the sacrifices and offerings, with his death). With the benefit of hindsight, of course! During Jesus' life, there are no references at all to Daniel's 70 weeks; it is reasonable to assume the Jews weren't counting down the years and expecting the end to be within the next generation! After all, "sevens" in biblical context also have the symbolical meaning of completion; God created earth in seven days. Only after the destruction of Jeruzalem has this timeline been put into the context of "sevens of (360-day) years", and the Abomination as something other than a sacriliegous Roman or Seleucid conqueror.
But how to explain the "gap" of the prophesy, since the 70th "week" still has to come? With the benefit of hindsight, it is usually said that, because the 70 weeks were decreed "for your people and your holy city", and, since with Jesus' death the covenant between God and Israel has been broken, the appointed period has been broken up as well; in the 70th "week", there will be made a "strong covenant", implying that there wasn't one before, or that it has been broken, which would be the case with the events after the 69th "week" of verse 26. Only with the creation of the "strong covenant", which happens sometime after the war and destruction of Jeruzalem and the Temple, does the final phase of the prophesy begin. Here's a chart I shamelessly stole from some site:
Is this convoluded? Absolutely! But it's as much an explanation in hindsight as the "490 years after the decree to rebuild the temple" is; in Jesus' time, there is no notion of the prophesy being fullfilled within those 490 years, otherwise it would've been brought up during the New Testament, but apparently this isn't considered relevant at the time. On the contraty, one could consider Jesus' prophesy that the end will only come after the "gospel of the kingdom will be preached in the whole world as a testimony to all nations", as an indirect reference to the "strong covenant" of the 70th "week". Otherwise he doesn't say anything about being anywhere near that point in time.
But if at some point in the future Israël would suddenly turn to Christianity, that would be a point of concern, yes.