I'm not really sure how you quantify accumulated hype.  Mario Kart Wii did about 2.1m across its launch weeks on a console with a 24 million install base (25.5m by the US launch week).  On Amazon, Mario Kart Wii was 11th for the month of March in 2008, MK8 didn't make the top 100 for March 2014.  In April MKWii went up to number 3.  MK8 should make it in for April, but seeing as how it is currently at 27, I don't see it making it to third.  MKWii hit number one (Wii wheel number two) for May.  The market was also quite a bit bigger in 2008 which would exacerbate placement differences.  Now Amazon is just one retailer, and I am only looking at the US site, but it certainly isn't pointing towards a 1.5m launch week.

VGC preorders (which admittedly aren't worth much) aren't looking like such a strong launch either.  1.5m WW would likely require around 700k US at least.  No Wii U game so far has gotten even half of that, and only 4 have sold that lifetime in North America (three of which have been bundled).  If MK8 has the same launch ratio that Galaxy/3D World had, we'd be looking at ~280k in the US.  Though I think it can do better than that.

700k first week, 5 million 2014, 12 million lifetime.

On a related note, when MK Wii released, MKDS got a huge, prolonged sales spoke. Does anyone think the release of Mario Kart 8 could have a similar impact on Mario Kart 7 sales?

First week: 550,000 copies

2014: 5 million

Lifetime: 10 million

I really couldn't even begin to make a prediction I'd be confident with because there are so many variables to consider, at least regarding sales early on.

If Ninty doesn't give the game proper advertising and doesn't bundle the game (basically what happened to DK) then I don't expect a whole lot. That would amount to $299 + $60 for new consumers.

If Ninty advertises well and bundles the game for $299, I think sales will be fairly impressive.

However, if they were to bundle the game and drop the price to $249 (not likely, unfortunately), then sales would be through the roof and likely remain strong throughout the year.

First week: 400 k

2014: 2.5 million

Lifetime: 5 millions.

looking at how well infamous sold in 2 days and titanfall did in a week with less install base than WiiU I'd say people are greatly underestimating this game's potential sales.

FW: 340k
2014: 1.75 mil
Lifetime: 6 mil

First week WW: 400-500k
2014 WW: 2M
Lifetime WW: never above 4M

500k first week
2014 - 3m
Lifetime - 8.5m

800,000 first week.
4.5 million 2014
11 million lifetime.