Wherewas jonas and gabriel are going on the sled.what is their ultimate destination?

We really don't know. We are given the vague sense that there is something at the bottom of the hill but we are not sure what. We find out by the next book but I won't spoil it for you. I recall hoping it was a nice society or village when I finished the book.

Elsewhere. In elsewhere, jonas can experience everything that you or i would experience, not ruled by a community