I believe that the American Wii U sales will be more than the world wide GC sales when all is said and done.

I say this because of a few reasons:

1) Nintendo's series have grown since the GC despite what people want to think. Yes, the DS & Wii had huge sales which in return pushed games. Yet, it is obvious that certain games have reached a larger audience, increasing potential buyers. This is why Mario Kart 7 for example has already outsold its GBA counterpart despite the 3DS having significantly less sales so far. Mario Kart 8 will be much bigger than most people on here expect.

2) The gaming industry has grown and is now much bigger than it was in 2001. This alone will help with sales in the longrun.

3) The Wii U is still $300 which is more than the GC's launch price. It will be lowered eventually and this will increase sales. 

4) The GC never had an add-on while I fully expect the Wii U to have either that or a redesign which should help push sales.

thoughts? 

I think Xbox One america sales>> Wii U total sales by the end of the year. And to answer the OP, I think your prediction is wrong. I can only see Wii U selling 20 million total worldwide

thoughts? Absolutely not. Wii U is below US only GC sales already. In order to pass GC WW sales it wit US only it would kinda... you know, sell more than GC

The Wii U needs software more than anything else, and a new Mario Kart or Smash Bros is only going to go so far, especially if said games are still hampered by Nintendo's network infrastructure compared to their rivals. Both of these games should have a shit ton of online multiplayer modes and options, and not just limited to the most basic of modes and virtually non-existent lobbies and matchmaking options like their predecessors on the Wii were.

Woah dream big!

When has an add-on or peripheral ever been successful? I would even argue that peripherals are part of the reason why things go wrong for console makers... Sega would like to say hi.

I think it will cause I still believe (I wont if 2014 sells worse the Gamecube's second year) that the reason the wiiU is selling this badly was due to a series of unfortunate events such as a lack of advertising for 8 months + after the release of the wiiU, bad press, no e3 show, terrible name and most importantly, lack of steady first party games...

2014 is looking to change that since they have started advertising last November and a steady stream of games are gonna come including MK8 and Smash Bros and etc... Without going into too much detail and before people quote me to say I am wrong and am an Idiot... If the wiiU doesn't =/surpass GC's second + first year combined sales by the end of 2014, then I would say its dooooomed

...doesn't a console have to at least be tracking higher in said region to sell more than another console WW?

Hahahahahaha! You can "Think" all you want, but the fact is the Gamecube is selling better. Nothing to support your claims. Can Wii U make a "Comeback?" Yes. But it will be coming back up to Gamecube sales.