To be sure the generation names have been applied by the owners and not by the oem. As with any car, not just a Viper, a new generation is generally a significant styling change, generally including a new chassis. From 1995 to the 1996 coupe that did occur. The suspension (chassis) was revised from steel tubular to aluminum. The stying changed, not only with the introduction of the coupe, but also with a new front fascia and hood. It also received a completely new interior. It also received a new engine and driveline components. I believe that consitituted a generation change. If we ignore that some of the changes were brought in early in the 1996 RT/10 the generation change would be clear.
For 2003 there was new styling, new interior, new engine and driveline, etc. Clearly a new generation by any standard.
Now for 2008, from what we hear, we have a new hood, revised driveline and engine. That is not enough to constitute a new vehicle or generation to me.