Reacting to the 4 seat '58 Thunderbird?
That's a good point and it could very well be true. Clearly, it seems they eventually decided to continue a 2-seat Corvette (and then Corvette Stingray). But perhaps there were already thoughts about a future pony-car/4-seat/Camaro-type Mustang competitor vehicle in the works
Maybe a thought or two of giving the Cadillac line a Vette of their own. Not too dissimilar to the Cadillac XLR.
The future of the Corvette was very much in doubt during this time frame. The bean counters were using 10,000 units as the benchmark for annual production if the model was to be continued...in 1960 they finally reached that level with 10,261 being made. Ford's success with the four passenger 1958 models had GM seriously considering the Corvette becoming a four passenger automobile or drop the brand entirely.
Those are all very good points and observations. The two cars closer to the camera seem to be clays and the background Nomad-type vehicle seems to be perhaps a production-type automobile.
