No one here can tell you how the book ends.  It has an ambiguous ending.  This means that each reader has to determine what happened.  There are clues along the book, especially at the end, but each reader has to determine what they mean.  My students usually seem to be evenly divided between those who think that they escaped and those who think they died.

I had always thought the ending implied that Jonas and Gabe had frozen to death. It just seemed too unlikely that they found their way to a new place, when they were so close to death. But in Messenger, a "companion" book to both The Giver and Gathering Blue, Jonas is, ten or so years later, the leader of his new community.

The book ends as described above. The challenge of that ending is that every reader is enabled to continue the story, in his/her own mind, as s/he interprets the situation and the circumstances. It's up to you to decide if you think Jonas and Gabe survive, finding a new community that has not given up the differences and conflicts of a world similar to ours for the sameness and security of the community which they left.

Jonas runs away with Gabe to save Gabe.  They run for a long time and are about to die.  It's snowy and they come to a hill.  There's a sled.  They sled down the hill towards a village where there are lights and people singing.  It's like in the memory Jonas got.