No, in the past, it has always gone to the next thread below on the forum list, which would be the thread with the next most recent post. Similarly, for previous thread, it has always gone to the thread listed just above on the forum page, which would be the thread with the next most recent but earlier most recent post.

If you haven't visited a forum for a while, you go to the top thread after all of the sticky material, look at that thread, and then keep clicking "previous" until you've seen all of the new material in the order that threads are listed on the main page for the forum, which is ordered by the most recent post, not by when the thread was created. For example, if something has been added to a sticky thread, I see that one in the order it would be if it weren't stickied. And if someone has posted recently in a lounge thread, going through clicking either next of previous gets me to the lounge thread where it is in the list. Otherwise, since the lounge threads are generally many years old, one would never see new posts there by clicking Previous or Next.