This seems like a Bad Idea to me - at least if it's intended to replace the existing code block format.
My main objection is it breaks the ability to cut and paste from a code block to your terminal: If you cut and paste something with the above formatting it is virtually guaranteed NOT to work (it can be "fixed" of course, but reassembling the original text would require at minimum some scripting. That's asking a lot of people...).
My secondary objection is that without a quantum leap in AI technology it's impossible to intelligently break lines in all of the possible "stuff" that gets put in code blocks: Doing so requires context awareness that the site doesn't have ("Is this a log file? An error message? A C program? A shell script? Python? Perl? Ruby?")
The Right Thing (IMHO) is for whoever is posting this data to properly format it for us (break long lines themselves). This isn't that much effort - I'd say it's the minimum we should expect from someone asking a question ("Make your question readable"), or posting an answer ("Break long lines sensibly so your answer is readable").
I don't really object to this as an additional format, though I doubt people would be using it much (the markdown formatting options are already numerous enough that most people don't know them all) and I don't personally see the need for it either (again I feel the onus is on the person posting to make their post readable)