If the past is any way to predict the future it will be around for a few more years...most versions of the Z have a five year lifecycle. There are small changes made throughout each version but five years looks like the average lifespan of each, jut look at the 350Z - over its six year run there were three different engines (four if you count the Japan only 380RS).
All that being said, I wouldn't rely on past history alone. You also shouldn't necessarily concern yourself with having the lastest Z, they're always going to tweak and change the car. I was completely happy when I picked up my 35th Anniversary Z...and then Nissan released the 2007 with the HR engine.

I'm sure all the drivers that bought the last of the 2008's felt the same way when the 370Z came out though.
Still, it's pretty early in the cycle of the 370, I don't know that much will change very soon. But I'd sure love to see a more retro gauge cluster and no more boomerang lights!
