I think in 5years time if you really want a supra, buy a vvti supra with a good spec from japan(700bhp with awesome brakes and suspension set up with 6sp:D) and just add some personal touches to it. You should still have lots money left for enjoying the car on track etc.
I'am sure supra's will still be turning heads in years to come.
But if you want a beast of a machine in 5years time the gtr seems to be the better choice especially by then there should be lots of tuning parts out. It would definetly be a better and faster car than the supra would be but I still love supra's.
Just save up and see how you feel by then, you never know you might like german cars by then or the fuel prices become so high that you just buy a fast super bike to have fun in.
I do think people will love older cars as the years go on, there a great resturation project and seeing a old car look like new and going faster than a new car is f**king amazing I think.