It has been brought out from someone from Official Nintendo Magazine that the Wii U version of Sonic & All-Stars Racing Transformed will not have any Miiverse functions. Here is what he said:

Spoke to a Sonic & All Stars Racing dev today. Confirmed no Miiverse stuff, said they learned of it too late

I guess Sega learned about the Miiverse capabilities of the Wii U too late so they didn’t have time to input any specific features for the Wii U version of the game.