I think the biggest question you have to ask is whether or not you are happy with the Gen IV? If you are happy with it, maybe it's not worth it.
My style is more, get something different. I started with a Honda S2000, then thought, "Man, I'd really like a cool car to drive in the winter." Our winter is wicked and long up here in Canada, so a cool winter car made sense. I kept the S2000, and bought a WRX STi, which I've modded heavily. That car rocks, but then I thought, "I need a 'man's car' for the summer", and the search went on for a year and a half, I kept the Honda and Subie and picked up the Gen V GTS. Which I absolutely love, and of course is a far superior car to the other two, but they have their advantages (my wife drives the S2000 now and seems to like it). Next on the horizon, I think I'd like something European, perhaps a Porsche, or a Lotus Elise, I'm not sure......
If you like to have variety, and you really like the car you have, I'd just find something else to set your sights on. If not, you can't go wrong with the Gen V. It is fantastic.
