The 300ZX is an icon. It does look still to this day every part a modern car and has truely stood the test of time. That being said I don't think it looks nearly as curvacious as the 350Z and no where near as as curvy as the 370Z. It truely is an amazing vehicle. Still highly sought after even by people who weren't even born when it came out
The 370Z is an outstanding Z car in both form and function and on that alone it will stand the test of time. Who knows what design ques cars ten or twenty years from now will take - the 370Z may follow those lines or cars may look like boxes by then. Regardless the 370Z has what it takes to be outstanding now and that's unlikely to change in the future.