The defender has never been fitted with air bags, or any side protection. So to get them to pass any real tests would need a total redesign.
Add the fact in it's current guise it will never pass up coming EU tests and the huge labour cost to build one and your faced with either redesigning it, or killing it off totally.
Given how it's the halo model of LR, option 2 would never happen. But because of it being the halo model, getting the new design right is going to be a huge risk as you can't please everyone. So you need to take the majority and they will be trying to crack the US again with the new one and i would imagine the Jeep would be seen as it's main challenge.