I also asked my dealer when the PHEV version of the Defender will be available. He said they keep getting the runaround from Land Rover. When the PHEV version of the Range Rover and RRS came out a few years ago, they got around 5 of them that they sold right away. They had customer orders for almost 20 more, but Land Rover pulled the plug (pun not intended) on the model and they couldn't get anymore.
Right now, the Jeep Wrangler "4Xe" is the top selling hybrid vehicle in the U.S. Land Rover is missing out on a major market.
Unfortunately, looking at all the press stuff for the Defender PHEV, it looks like Land Rover is marketing it as a performance vehicle and not a simple Defender that you can run full electric for 30 miles. I'm sure that means no 18" wheels (without mods) and prices similar to the V8 model.