Because when OSX n+1 is released, it's immediately impossible to get any work done on OSX n? No - but the same logic applies to application software, right? If

Because when OSX n+1 is released, it's immediately impossible to get any work done on OSX n? No - but the same logic applies to application software, right? If SuperApp m+1 requires OSX n+1, surely you can continue to get work done with what you have now - SuperApp m running on OSX n? There's no reason for developers to handicap SuperApp m+1 by avoiding all OSX n+1 APIs...