Q: When will iTunes U, be available for Macbook or iMac computers?

As you already know, these are user-to-user forums, you're not talking to Apple nor iTunes Support on here - we won't know if/when iTunes U might become available on computers until if/when Apple announce something. If you want to leave feedback to Apple about it : http://www.apple.com/feedback/

From my reply to

Will iTunes U ever be an App from the Mac App Store?

The iTunes U student experience is only available for iOS.

The teacher experience is available on iOS and the web:

     https://itunesu.itunes.apple.com/coursemanager/

If you are a student, I suggest you tell Apple about your need:

     http://www.apple.com/feedback/itunes-u_ios.html