Coming from a customer service rep...
Thank you for taking the time to write with your questions regarding a Wii U Ambassador program. The Ambassador program is only available to any Nintendo 3DS owner who purchased their system before August 12, 2011 and there are no plans for a similar program for Wii U.
I know that this isn’t what you were hoping for, but we appreciate your support of our products now and in the future. I also want to assure you that your comments will be added to our records and made available for other departments at the company to use as they see fit.