What makes you say that? A bigger install base implies a greater likelihood for better sales. If the Wii sells better than the 360 and PS3 combined, its install base holds the prospect for far better sales.
As it stands right now, the Wii sells more than the 360 and PS3 combined on a weekly basis (~230k vs. ~150k). If it weren't for the 360's head start, it would already be far ahead of the combined total.
For the record, the PS3 attach rate is pretty poor at the moment, the 360's is doing well, though. So yes, the 360/PS3 attach rate is better, with no help from the PS3.
PS3: 5.51m/51w, avg 108,039/w (up 239)
360: 12.93m/102w, avg 126,764/w (up 625), leads PS3 by 7.42m (up 70k), avg lead 18,725/w (up 386)
Wii: 13.52m/51w, avg 265,098/w (dn 1,102), leads PS3 by 8.01m (up 90k), avg lead 157,059/w (dn 1,341)
If 360 sales stabilize, PS3 sales increases needed to pass 360 by...
01/08: (008w) +875.8%, 04/08: (021w) +344.4%, 07/08: (034w) +219.3%, 10/08: (047w) +163.5%
01/09: (060w) +131.8%, 04/09: (073w) +111.4%, 07/09: (085w) +098.1%, 10/09: (099w) +086.7%
If Wii sales stabilize, PS3 sales increases needed to pass Wii by...
01/08: (008w) +1072.%, 04/08: (021w) +498.4%, 07/08: (034w) +363.4%, 10/08: (047w) +303.1%
01/09: (060w) +269.0%, 04/09: (073w) +246.9%, 07/09: (085w) +232.6%, 10/09: (099w) +220.3%
If PS2 sales freeze, Wii sales increases needed to pass PS2 (as of Mar07, 108.4m) by...
2008: (008w) +4373.8%, 2009: (060w) +0496.5%, 2010: (112w) +0219.6%, 2011: (165w) +0116.9%
2012: (217w) +0064.9%, 2013: (269w) +0033.1%, 2014: (321w) +0011.5%, 2015: (376w) -0004.8%
At +0% it will pass it in 358w, the week ending September 19th, 2014, at an age of 409w (7y44w).
Current age of PS2: 7y37w.
Last update: Week ending November 3, 2007
