It's all about overcoming engineering hurdles and production costs.
Although it was previously denied, Dodge engineers are still reportedly looking for a way to transplant the new 6.2-liter supercharged Hemi V8 into the engine bay of the Viper. We reported that, according to Dodge, it wasn't technically possible to make the switch due to the Hemi's tall cylinder heads which wouldn't fit under the Viper's low hoodline. Furthermore, the V8 was too wide and unable to clear the Viper's chassis rails. Still, 707 hp compared to 640 sounds mighty tempting.
According to Allpar, a pair of supercharged V10s have been delivered for initial testing. Presumably, 707 hp can be achieved and even surpassed, and if the block, internal parts, transmission, and body can handle it, then 800 hp is even possible. The idea behind all of this is to rekindle lagging Viper sales and to put the car ahead of the Corvette in direct performance spec comparisons. So why stop at 800 hp? Is 1,000 hp possible? Probably not, because this would require a new gearbox and differential as well as plenty of additional cooling upgrades. Perhaps a new body would even be needed to deal with the stresses. Production costs would also go through the roof. We'll have to wait and see if these issues can be overcome.