Here's an article addressing something I've been wondering: the chassis of the new Defender probably cannot accommodate a truck body.
https://www.motor1.com/news/364402/land-rover-defender-truck-possible/
The article quotes the GM of Land Rover Australia as saying that a Defender truck is under consideration, but would require a partnership with another automaker.
I take this to mean that, if there's ever going to be a Defender truck, it's going to be on a totally different platform than the new Defender, which probably means it's never going to happen.
The article doesn't mention it, but for a truck to even be remotely competitive in the U.S., it has to be manufactured here, less the "chicken tax" price it out of existence. As far as I know, JLR doesn't make anything in the U.S., so the "partnership" with another automaker would probably have to entail the other automaker building the whole thing stateside.