The rule has always been you lose a huge chunk of the value just driving a new unit off the lot.
The rule is it cost nothing to keep it another year, but cost the price of the new unit minus the old to get another one.
In this RV-hungry market you can just sell it yourself, trade-in would lose you more money unless you can burn money and are just that incapable of selling something.
It is always cheaper to hang on to it another year, then another year, until you HAVE to sell it.
Unless the layout is just wrong and you are not enjoying it, keep it.
The sweet spot for trade-in is to trade it in at the very last moment that the dealership will take it for its age.