Lets insert a little logic here.
First and foremost, these are sales in Japan. Look at ALL of the numbers. The country is currently a wasteland for console sales. If you were expecting much more than that boost, you were, quite frankly, being dumb.
Second, "Opening Week" for Mario Kart 8 sales/hw boost in Japan will be divided over two weeks. This release only covers 3 days of sales, the next 4 days of week one will be out next week.
Third, the Japanese market didn't get such an amazing deal. Western gamers had the Mario Kart bundle + the free game. If you want to cast doom and gloom do it AFTER we see the worldwide totals, because not only should you expect Japanese sales to be garbage across the board, but the Western sales should be decidedly more vibrant due to the larger amount of customers and the much, much better deal.