Since people would start to want to buy cars more frequently because of the constant increate in performance/features (which the article is saying will be faster than the current state of motor innovation), would the car manufacturers be able to offer lower-cost models that would be bought every 3/4 years.

They could recoup the money from cheaper cars from the faster purchase cycle.

Or else move to a leasing model (this is becoming more popular with people I know in the UK, Ireland).