To find the average population growth over 5 years, we can first determine the average annual growth based on the growth over the last 2 years.
The town's population grew by 600 people in 2 years. To find the average annual growth:
\[ \text{Average annual growth} = \frac{600 \text{ people}}{2 \text{ years}} = 300 \text{ people per year} \]
Now, to find the expected growth over the next 5 years:
\[ \text{Growth in 5 years} = 300 \text{ people/year} \times 5 \text{ years} = 1,500 \text{ people} \]
Thus, the town is expected to grow by 1,500 people in the next 5 years.