I really don't believe that a console can have dramatically stronger sales later in its life unless it starts out against remarkably weak competition ...
If you look at the PS3 currently it has both started off selling really poorly and also has a very low attach rate (in particular in Japan), suppose for a minute that this trend continues through 2007 and 2008 (while the PS3 is still very expensive compared to the competition). Third party developers are only going to tolerate sales that are below expectations for so long, and these developers are likely going to reduce support as games sell poorly.
In 2009 when a consumer walks into a store, sees a $129 Wii and a $299 PS3, takes a look at the game rack and realizes that the Wii has 5 times as many games available which console are they going to buy? This is the exact same problem the N64 faced against the Playstation; the original Playstation produced games that were far uglier but because the Playstation had far more development (and lower game prices) most people bought it instead of the N64.
