First, I don't think Tesla could do it today for $100-120K. Yes, the battery tech has improved, but in order to do it, they would virtually have to re-invent the car. With the next gen right around the corner with SC capability, longer range, etc, I just don't think there would be the demand...
Now, if we're just going to create the new car out of thin air with a new R80 battery, there could be some folks who would be interested simply because of the lower price, but since the model 3 is faster and can hit the SC, with more range, why would anyone realistically do it?
It would devalue, perhaps not huge amount, the original version simply because of age in comparison, unless it was a signature or other special version...definitely would put a cap on the value, though.