1. must hit a ceiling and the rate of increase will significantly slow,
2. or Bitcoin mining will break SHA-256 and render it insecure.
I find 1 to be a the most likely outcome however the most plausible path for 2 would be a novel cryptanalytic attack on SHA-256 which could be exploited to increase mining power. It seems very unlikely that 2 would occur because mining power approaches the brute force limits of SHA-256.
1. must hit a ceiling and the rate of increase will significantly slow,
2. or Bitcoin mining will break SHA-256 and render it insecure.
I find 1 to be a the most likely outcome however the most plausible path for 2 would be a novel cryptanalytic attack on SHA-256 which could be exploited to increase mining power. It seems very unlikely that 2 would occur because mining power approaches the brute force limits of SHA-256.