The Viper comes from the factory with headers already installed. Granted, they may not be the best performing headers available, but definitly better than manifolds. So from the collectors back is all you would really have to swap. And I agree, it will be more expensive to modify, but with two vehicles on the market with the same engine, the price of parts will drop slightly due to higher demand, and most of the Vipers I have seen were modified in some way, so I'm sure there will be more than a few owners modifying the SRT-10 as well. Most people aren't satisfied with stock performance no matter how good it is.
There is always going to be someone faster than you. All it takes is money. Like I've said before, Speed costs money. How fast do you want to go??? For some, the SRT-10 Ram is right up their alley for performance and potential.
And it looks like Mike 38SC has confirmed my guess that the new Lightning will be comparably priced to the SRT-10. One guy in my Dakota R/T club just bought a new SRT-10 for under $45K, and another was offered one for $40K from a dealer. Most dealers are putting huge dealer mark ups on them though, and $60K after dealer markup isn't unheard of, and I've heard of one listed at $70K. Worste part is some fool will actually pay the price too.