The key space is 2^256. Do the calculations for someone running 1 million instances of 1 million tries per second. How long would it take for someone to find a key assuming that there are 2 billion keys currently. There is tons of math being done on this, so it might be better to just google it first. We would've done something about it if it is really a security risk.
Rate: 1,000,000 * 1,000,000
Key space: 2^256
Number of keys: 2,000,000,000
Ps. That is still many many times of earth's existence.