ohhh ... I think I can convince you that hybrid acceptance may follow an exponential growth rate; if all you require is a power function that is quite a bit less in total than what you yourself anticipate ..

How about 1% more hybrids every year than the year before, for the next 10 years ? This would mean that the current 100,000 Prius sold, e.g., jump to 114,462 Prius sold in year 10. As an exponent, for your amusement: f(x) = 1.01^x

As I explained above, logs are not necessarily asymptotic, and power functions can be. But I was not prophesizing 2^x growth; I only pointed out that if it happens like the GM exec was considering, he will be unemployed well before his retirement.