Do you really think the developers would do that? Put bitcoin in jeopardy and many mining farms out of business?
The "developers", whoever they might be, cannot change the difficulty.
It is unfortunate that so many people believe that the "developers" actually have some sort of control over Bitcoin.
As far as SHA-256 being cracked, it would not affect mining that much.
It is extremely unlikely that an inverse of SHA-256 will ever be found. That has never happened for any hashing algorithm. A realistic scenario would be that a weakness is found that would make it easier and faster to solve a block. If that happened, then it would simply mean that people might be able to start mining on CPUs and GPUs again until ASICs could be developed to take advantage of the weakness. The difficulty would rise and Bitcoin would continue.