The way we look at is there is no way to guarantee the value from now through time of delivery. The biggest factor to that is actually market conditions, what are vehicles actually selling for, as opposed to your individual vehicle's miles on the odometer. Mileage is easy to estimate or adjust for. So we do what is called "TODAY" value meaning this is NOT an estimate of what it will be worth at an unknown delivery date, but rather if you wanted to bring it to us today, this is what it's worth.
Now we usually recommend don't even think too much about that until the new vehicle is in transit or at least production. That way you know you're about 3-5 weeks out so EVEN STILL the value is not lockable, you have a closer range of real life. BUT you still have time to react if you choose not to trade in.
You end up balancing the difference between trading and selling on your own considering
- Distance/time/cost to get the trade vehicle to the dealership
- Sales tax savings, if your state affords that
- Time savings compared to selling it outright on your own
- Market conditions in your area versus dealership location
- Vehicle fit for dealership/location (no one is looking for a Prius at Mark Dodge...)
Ultimately you have to make the best choice for what makes sense for you - but you won't have all the info until the new truck is nearly ready.