It should pass PS1 rather easily to be honest.
Nintendo is still set for a big Oct-Dec quarter (DKC, Kirby, Wii Party, and then Epic Mickey, Goldeneye, Sonic Colors, Udraw, NBA Jam, Dj Hero 2, Just Dance 2, Def Jam, Michael Jackson, etc for the West) with Wii.
The current fiscal year projection is 18m. If you figure 3m / 3m / 9m / 3m by quarter its relatively easy to make, and what Nintendo has in mind, give or take 5% per quarter. I could see them only doing 17m or something, but its still a damn good year. Last fiscal year was more like 2.2m / 3.5m / 11.2m / 3.5m (20.5m for year to March 2010) - so its essentially flat non-holiday quarter sales (up on the price cut for the June 2010 quarter, down in Sept 10 / March 11 quarters without the price cut) and down a couple million in the Dec quarter because of fewer massive titles for Christmas / no recent price cut.
Heading into 2011 though, you have to figure there is another price cut by Fall. So the next fiscal year could be 2m / 3.5m / 7.5m / 3.0m or something. That'd be 15.5m. It isn't really that hard to imagine Wii seeing one more real good year at $180 or $150 - especially with Zelda likely for Christmas, Mario Sports Mix for April, Pikmin 3 for June, Wii Relax for August, or something. The western developers won't give up on the Wii base until the third party market is less than 30m year and it won't reach that point for a few years yet.
All of Nintendo's top teams should be done with Wii by the end of March 2012 though - and so after that point it should begin to decline rapidly.
But it could easily get to 120m
LTD Projection for 3/2011 88.93m (18m in Fiscal Year ending March 2011)
3/2012 LTD: 104m (15m - price cut early in FY to make Wii a good value against Kinect / Move, and Wii successor)
3/2013 LTD: 114m (10m - no price cut, Wii successor / Kinect / Move / PS4 / X720 all possibilities)
3/2014 LTD: 122m (8m - price cut to $100...still includes two games - purchasing rates rapidly drop well below 1/2 game per average user for non bundled titles, last big Christmas for Wii)
3/2015 LTD: 126m (4m - newer systems approach mass market pricing)
3/2016 LTD: 128m (2m)
3/2017 LTD: 129m (1m - production stops)
People are difficult to govern because they have too much knowledge.
When there are more laws, there are more criminals.
- Lao Tzu
