Looking at historical sales trends, I think SM3DW will most likely come in #2 next week in the U.S. charts among all console games, being beaten only by the 360 port of COD: Ghosts, and will be the best-selling system exclusive this holiday here in the States for any console. My evidence? Well, let's look at how the predecessors to all the best-selling games did. First, a relevant chart:

Currently, COD: Ghosts is the best-selling game right now on all platforms. However, COD games are extremely frontloaded in their launch holidays. The last few COD games to come out experienced a decline in sales of 80%, plus or minus a couple of percent, from their first week to their second week, and Ghosts is looking to be no exception. The 360 port experienced and 78.7% drop, the PS3 port a 77% drop, and the PS4 port a staggering 89.3% drop. In all likelihood, the XBO port of COD: Ghosts, which was the #1 game of the week ending the 23rd, will suffer a similar drop. With sales of over 495k that week, it could drop to anywhere from 163k to under 54k, depending on whether its curve is more in line with the seventh-gen ports or the PS4 port. As for the other big-name AAA multiplat action games like Battlefield and Assassin's Creed, they likewise have steep drops their second week, selling only a third to a quarter as many copies their second week (and the PS4 ports of BF4 and AC4 also had much bigger drops than the 360 & PS3 ports did, which could signal a similar drop for the XBO port).

Meanwhile, Mario games tend to not be that frontloaded. While Galaxy and NSMBWii both had modest launch weeks by American standards, they did quite well throughout their debut holidays, with farm shallower second-week drops compared to the bigger AAA action games. Galaxy declined by only 39.5% in its second week in the U.S., and NSMBWii by only 38.6%. So, assuming 3D World experiences a similar 39% drop for the week ending the 30th, it will sell between 145k to 150k. This is already well above where the 360, PS3, and PS4 ports of AC4 and BF4 are right now, and given how far the PS4's exclusives dropped, which was similar to the drops experienced by the big multiplat games (more on this in a bit), it's likely that the XBO's exclusives will each sell at most around 50,000 copies in their second week, give or take. That leaves Ghosts. While the PS4 port of Ghosts is already well below 100k and the XBO port will likely do the same thing, the 360 port will likely still take the #1 spot next week, leaving it up to the PS3 port to challenge Mario for the #2 spot. Assuming comparable curves to their predecessors, the PS3 & 360 ports of Ghosts will experience a decent drop for that week, perhaps another 30%, give or take. That will not enough to keep the 360 port from losing the #1 spot, as it will likely sell around 200k. However, the PS3 port could drop to below 140k, putting it in third just behind SM3DW.

So, there's a very high chance that Mario will be the second best-selling console title, and it will definitely be in the top three, as well as be the best-selling eighth-gen release for the week. But what about the holiday as a whole? While Ghosts, BF4, and AC4 are multiplat and cross-gen and will thus be the top 3 games this holiday, amongst all exclusives Mario will likely take the top spot. It already beat Ryse, Forza 5, Dead Rising 3, and Knack in first week sales, and its second week sales will likely blow those other games out of the water. That leaves Killzone, which had the biggest first week sales figures of any eighth-gen exclusive in the States. However, it had a very steep drop in second-week sales just like every other PS4 game, with a decline of nearly 85%. Assuming sales stay relatively flat for the remainder of the year (~50k per week on average), it might end up with a total of around 700k copies. Meanwhile, if Mario follows a similar curve to Galaxy, it could sell close to one million copies. So, I think that it's almost guaranteed that Mario will be the best-selling system exclusive for any platform

Wait a second. A challenger appears. There's only one game that I think can challenge Mario for the #1 spot amongst all titles this holiday season, and that's Gran Turismo 6, which is the last major title for the year. However, it has the disadvantage of debuting a full two weeks after SM3DW. Assuming it has a similar week-to-week performance as GT5, it will have a far better first week than Mario and could end up selling close to a million copies in the U.S. Now, had it debuted a couple weeks earlier, it could have handily been the best-selling exclusive, beating Mario by perhaps a couple hundred thousand copies. Of course, if Mario still comes out on top, that's pretty impressive for a game on a system that will still probably have only about 10% the install base of the PS3 by year's end.

Of course, this is all just in the U.S. Gran Turismo will almost certainly be by far the best-selling system exclusive in Europe, and it could take Japan as well. Still, globally SM3DW may still take the #1 spot for best-selling game exclusive to an eighth-gen system. It'll all depend on how well everything does in Europe.