"We need to have consumers voluntarily go online with their Nintendo 3DS," said president Satoru Iwata, as part of outlining Nintendo's financial results for the latest fiscal year. "We are planning to do some promotional activities in order to urge them to do so."
The 3D version of Excitebike is part of a planned line of "3D Classics" for the eShop. The specific wording of the announcement--"certain period of time after the beginning of the system update"--suggests it might not happen as soon as the eShop goes live, but it'll hopefully occur soon after that.
At E3 2010, Nintendo had one 3DS loaded with classic NES games fitted with 3D visuals, including Punch-Out!! and others that have faded from my memory. I do remember they looked pretty rad, as the layered nature of old-school visuals present immediate rad-town benefits when given the 3D treatment.