At the time the authorities estimated the population to be 3000 frogs. Now five years after first being introduced to this area the population is estimated to be 196000 frogs. When will the population reach 2 000 000 frogs?
Insufficient data! with only two factual points and no indication of the probable shape of the curve (linear, quadratic, polynomial, exponential, etc.) you cannot extrapolate a third point.
You either need a know curve type or more data in order to make a mathematical extrapolation.