Case manufacturers and potential new MacBooks: Canaries in coalmines?

img.jpegEvery few Keynotes we get emails from case manufacturers encouraging us to keep an eye open for new case designs. For example, one designer told us today that they would be ready to ship on Friday “if Steve Jobs announces a new laptop.” While we know this is more conjecture and making-up-stuff-ure, looks like the first folks to be hit by a hardware refresh — case manufacturers — are getting pretty proactive. Is the Air for reals?