It might still come. We never had questions until fairly recently with DS4. But now we get lots of questions, such as "what is inside of stars", "why is water liquid" etc. . We tended to give age-inappropriate answers, often wondering if it was too much info; now that we know his test results, we think it's probably just right.
DS2, on the other hand, is asking questions now - probably imitating his brother. But he already asked questions like "what's that" in books much earlier, as a 1 year old.