"Arrow" the TV series is based on the Oliver Queen's transformation from being a horrible person to a hero who will be known as the Green "Arrow". The journey has been chronicled through the course of the the 5 seasons by showing scenes from his 5 year flashbacks of Oliver Queen's survival ordeal while being stranded in an island interspersed with his present day adventures in Star City. It's been known for awhile that "Arrow" will end with the scene of a bearded Oliver Queen running towards his salvation from being stranded on an island, returning from the scene the series began with. However, with the unexpected success of the series, "Arrow" will not end the way it was intended to be.
In a report from Cinmablend, "Arrow" showrunner Marc Geggenheim has this to say, "It was really just a hope at that point that the show would run five years. And we always thought that we would intercut the final moment of the series with the first moment of the series, that it would form one big Mobius strip." So it seems that the plans for series' end has changed. In addition, Marc Guggenheim spoke to TVLine and explained that the original plan was for the series to end with the first scene it began. But at that time, it was an early idea thinking that "Arrow" running for five seasons was a pipeline dream.
But now that "Arrow" has gained a massive following, the creative team behind the show has decided to scrap the original plan. "Arrow" is most likely running for more than five seasons due to the unexpected success. Writers will then have more room to play with the story and deviate from the initial plan. We can still expect season 5 to end with the escape from the island, but the show will still move forward from there. Reports have already indicated that the flashbacks will end this season 5.
The good news for fans is that "Arrow" will still continue onwards after season 5. The problem lies now with the series' writers on how they could seamlessly end the current arc with the new one. But if you ask me, that's a good problem to have.