With regard to consumer products, designers will always look for ways to reinvent the not too distant past and make it look fresh again. People love things that show a new way to look at something old. Like with fashion design and automotive design.
With technology, you have the military driving much of the progress, so practicality and cost effectiveness are the driving forces, not stylistic appeal.
Space ships and other futuristic stuff can have a military/practical look if you imagine them being used for battle, but if you imagine them being used by most people, then it’s realistic to try and imagine how designers would make something with appeal.
Old sci-fi stuff looks funny, but looking at a lot of it in the past month, I think it’s impressive that the space rocket designs and the space suit designs were accurate predictions of the future. I think it’s safe to take a military approach, because ‘practical’ will continue too look the same.
Your Jeep design will probably look dated some day because it uses contemporary vehicle design, but it will also look charming, because good design is good design, even after it goes out of style.
This subject is interesting to me. Off on a tangent, though.