The major limit to our long term economic growth will be our ability to innovate and to become more productive over time. We will never again be able to compete with other countries in terms of low priced labor, so we will have to continue to be on the cutting edge in terms of doing things in smarter ways.
Two things that could limit our ability to do these things would be our educational system and the amount of debt our government takes up. If we have poor education, we will not have as many people who will be likely to innovate new products or new ways to make products. If government has too much debt, there will be less money left over for entrepreneurs to borrow in hopes of making our economy grow.