Kirby & The Amazing Mirror is very likely, but Super Mario Advance 4 might not be.
Nintendo of America will reveal the full list of titles for Nintendo Ambassadors in the middle of August. The information will hit on or before August 12, the day of the Nintendo 3DS price drop in North America.
As it stands right now, a number of titles have been revealed for Nintendo Ambassadors including two titles that were not officially announced in the original press release – Super Mario Advance 4: Super Mario Bros. 3 and Kirby & The Amazing Mirror. Amidst a string of news reporting that these two games were not going to be released, NWR contacted Nintendo of America Customer Service to see what they had to say. According to the representative, Kirby & The Amazing Mirror is coming, while Super Mario Advance 4: Super Mario Bros. 3 was less likely to appear.
Nintendo Customer Service, while privy to some information, is by no means a definitive authority and this information should be taken in stride.