What do you guys think the typical 4x4 will be like 10, 20 years from now? What kind of engine will it have? Will it be diesel, hybrid, gas direct-injection turbo, E85, or....electric(!) What do you see as the main advantages or disadvantages of each in an off-road application?  

I sincerely believe that MY 4x4 of the future will a '42 Willys MB or a 97-06 Wrangler TJ. However, 4x4s of the future as a whole will likely be pretty different that what we're driving now. with the trend toward hybrid technology, uni-body construction, IFS, and AWD systems with full-time 4WD i think most future production "4x4s" will look like the Honda Element. Hopefully there will still be a few holder ons that produce some semblance of what we know as 4x4s today. Provided there is a Jeep Wrangler or Toyota FJ around we should be all good.