Ok luckily I actually kept the email, and didn't delete it:
Thanks for writing. It’s great to hear what you would like to see from us in the future, and I’m happy to document your comments and share them with other departments here at Nintendo.
I know that it would be great to tell you that a game like you have described has been announced and provide the release date. Unfortunately, there hasn’t been an announcement or even a hint of an announcement—so for now we have to assume that it doesn’t yet exist.
Of course, new products are revealed by us and our licensee partners throughout the year, so keep checking our website's “What’s New” section (http://www.nintendo.com/whatsnew) for the latest information and announcements.