There has been alot of talk about Mario Kart/Smash Bros being the games that drastically improve Wii U sales but im not so sure they will. Currently Wii U is tracking behind Gamecube and I believe that these two games will push Wii U sales to GC/N64 levels so about 20-30m.
I know alot of people will say "but Mario Kart Wii sold 34m!!!!!". The thing with that game tho is that it fell in line with the mass market/casual games like Wii Sports, Wii Play, NSMB Wii, Just Dance, etc and benefited greatly from that market that seems to have left consoles for Smartphones/Tablets.
As for Smash Bros, it sold 12m on Wii but this time it will also be on 3DS so that will likely take away some of the console versions thunder.
All in all I believe these games will sell what they did in the pre Wii era. Mario Kart on SNES/N64/GC sold in the 7-10m range and Smash Bros on N64/GC sold in the 5-7m range.
When the herd loses its way, the shepard must kill the bull that leads them astray.
