Personally, I think before long the early gen-3's are going to increase in value, or at the least, stay steady. Specifically, I feel they are going to be gobbled up by the owners looking to make BIG horsepower, and owners who have gen-3's now that are Supercharged (a LOT of them) are going to hang onto their cars rather than trade up when it comes out about how difficult making those horsepower levels will be on this new engine. This new engine and tuning system is going to be a nightmare for tuners, and with the VVT, there is NOTHING that can be done about its inability to be truly forced induction friendly, unless Dodge steps up and releases computer information- which I dont think is going to happen...ever. These new Gen-4 engines are going to become the kings of the Normally Aspirated segment however, perhaps up to around 750-800 horsepower, and even being fully streetable. Though for a lot of people... thats not enough.
The current cars are sorted out, we KNOW what they can do and how to build them, the aftermarket is already in place, and we are at the brink of having full control over Viper PCM's, up until the 2008 Venom Controller that is. Some new pieces from the Gen-4 engine will fit and fill in the gaps for seamless design of the ultra-horsepower cars built on the 03-06 platform. Other than the engine, the drivetrain changes are already available through the aftermarket in a bazillion combinations, pick whatever you want...its out there.