I think the real market is in a state of the art hardside pop up.. something with extensive aerodynamics research that is light and can be taken off/put on an existing truck. Gives the consumer more options on vehicle, and they don't have to have a dedicated "expedition" vehicle sitting around. You come in at a way lower price point than a full vehicle, so can reach more people.
The replies to this thread should be a red flag to the op... everyone has a different idea of what an 'expo' vehicle is. Many of the vehicles posted thus far are what I consider 'parking lot 4x4', ie not really going to get you that much farther up the road than a 4x2, mainly due to size, departure angles, etc etc.
I don't think the 'over landing' thing is as ripe as the OP seems to think. It was called car camping for a number of decades. Folks have been cruisng third world countries in Mogs etc for decades. It's been re branded for sure, and has the power of the web, and men with too much money and time powering it (like so many other fields/subjects online), but I'm not convinced there's a huge market out there clamoring for high end rigs.