Rare's newest Scribes page - a feature in which fans' questions are answered - discusses the possibility of Diddy Kong Racing on the Virtual Console and how far along Viva Pinata's development cycle is on the DS. On the issue of Diddy Kong Racing, the writer(s) for Scribes explains that in general, Nintendo does not want to change the appearance of VC games. Thus, that would probably mean Banjo and Conker would return (unlike the DS remake) if the game was released. However, Nintendo currently has no apparent interest to put the game on the Wii Shop Channel anytime soon and Rare believes the chances of the Diddy Kong Racing releasing in the future is "highly unlikely."
Also, although Rare didn't elaborate on the topic of Viva Pinata's completion, it was noted that the game is finished with development. Rare did not say when the game would be ready for launch, but because the game is no longer in development, one would expect an announcement of some sort very soon.