For the players who stick the world out to the very end, what could be a greater reward than being allowed to take one item with them to the next one? The Devs could allow hearthlings that have logged in for a certain amount of time towards when the world will reset the ability to take one piece of equipment or tool with them to the next world. That wouldn't include a high quality animal or workstation like a herbalists table. (Weapons I believe shouldn't be allowed as there would issues of griefing same issue with sledgehammers but that leaves axes out as well. A more experienced player would have a better opinion about that and I would love to hear thoughts on that below. I think maybe the condition the tool or equipment must be a 1x1 item would help remove lots of problematic items players could potentially have at the start.)
I could very easily see a lot of issues with this regarding fairness, but I think the true benefit would lie in increasing player activity potentially. With rumors of a new world on the horizon players may be enticed to return even if only for a short time. I think the idea you have to start over when a new world starts is always exciting, but having a piece of your old hearthling with you in the new world is an enticing way to encourage playing even in the late game.