Using console.error for warnings was silly in the first place. The solution to people ignoring warnings is to change that mindset, not to reduce the granularity of information and make everything red. I see the same thing with ESLint a lot.
For a long time, console.error had a stack trace in the Chrome devtools while console.warn didn't. I believe this was the main motivation to use console.error.
Ahhh, that makes a lot more sense!
I ran into this a lot with propType validations, which don't seem to be changing. But I'm in the camp that are "warning" should be displayed as a warning, so this is a welcome change. :)
Just FYI, propTypes is moved into it's own package and WILL be removed from React-proper soon.