Do you think it'll actually help user find new content or is it too convenient that users get lazier to browse around the forums to look for new content? I think there are pros and cons.
Pros are that it'll make those recent post/thread more accessible and maybe get users to engage in those threads quickly.
At the same time I feel like only those recent ones gets the most attention and leave other threads left to dust. Or when visitors visit the site, post something, come back an hour later and noticed those recent posts/threads are still sitting at the same position, they'll just come back some other time, hoping they'll be updated later or might think your forum is dead and quiet.