Don't really understand the number of cylinders concern. You can buy an Audi R8 with V-8 or V-10, same with Bentley. Porsche offers 4-6-and 8 and 10 versions. Ferrari seems to cover all the bases too. Most all auto manufacturers offer different engines in similar cars to address different marketing niches.
Viper already offers Verts and Coupes, ACR and SRT models. Traditionally they have the same engine in everything the offer, but no reason in the future the should not consider other offerings. I expect that someday they will also offer automatic options, as well as superchargers.
I am on my 3rd Viper, and for me it is no real consideration on the number of cyl's that are there for when I drive. Just want lots of HP, Torque, great handling, and a kick ass driving experience.
Yes, Viper's heritage has been with it's V-10. But things change, and to be successful you need to be open to change.
As long as the V-10 makes sense, and is viable, I believe it will be the basis of future Vipers, but someday...