Yeah it should be easy with little to no competition until late last part of the year.

Even if the next call of duty sold 25% of what ghosts did, it would still out sell mario kart.  Of course, there is no way the series is going decline anywhere near that much... Anything more than a 20% decline is unrealistic....

What happened to risk taking?

Well, that doesn't looks like an achievement.

The title says best selling Wii U game, dont know why people are bringing in CoD, so I would think so. The other potential competition is Smash Bros., but I highly doubt Smash will outsell Mario Kart, audience isn't big enough for that since Mario Kart appeals to a wider audience nowadays.

Mario Kart comes with a free game, which secures more purchases until that deal ends at the end of July. 

Assuming the overall sales stabilizes at 20% of the launch weekend every day while that deal is on (easier than having potentially exponentional growth starting this week given Mario Kart's reliance on word-of-mouth).

1,200,000 / 20% =  240,000
240,000 x 60

14,400,000 + 1,200,000
15,600,000

(LIFE TO DATE OF GHOSTS: 1,770,000 XO + 7,950,000 PS3 + 8,660,000 X360 + 160,000 WU + 550,000 Win + 2,250,000 PS4) = 21,340,000

80% of 21,340,000 (presumed active sales, games like CoD and Mario Kart are both nightmares for looking back, they sell you long-time, as it were.)
17,072,000 

20% of 17,072,000 (series decline assumption)
3,414,400

17,072,000 - 3,414,400
13,657,600

For simplicity lets say that COD's being multi-platform simply has the same as Mario Kart being released so much earlier on year end sales.

Might not seem too bold, but with NSMBU at 4M (a stunning 64.5%) attach rate, that would still be fairly impressive.

it will be.  its hard to find a copy allready, bundles are gone.  will be hard to sell 100k this week...

woh, so you are saying that mk8 is going to sell  300% more than the wii u hardware itself??  That is impressive my friend, very impressive

Honestly, the biggest barrier to mk8's continues sales growth is the install base of the wii u itself.  It certainly isn't going to sell 20% of its opening weekend on a daily basis...

If you predicted it before the 1.2M news, it still wouldn't be that bold. After that? It is just obvious. I think I will start a thread saying that Halo 5 will be the top-selling X1 exclusive game in 2015 or that GT7 will do it the year it launches.