With recent rumours circulating the 'net, something more solid has emerged with some nifty sleuthing from Codename Revolution. Fancy a dose of classic Sega with your Wii? Read for the first selection of Genesis titles available on the Virtual Console.
The list is presumably official as it stems from the ERSB website, the organisation that provides content ratings to games, where a search for "Sega" and Wii produces the following list:
Certainly some great classics from Sega! What other Mega Drive (Genesis) titles would you like to see on the Wii?
Stick with C3 for future updates...