http://vgchartz.com/hwcomps.php?cons1=Wii®1=America&cons2=PS3®2=All&cons3=Wii®3=America
Soon, unless demand for the wii sudenly falls off in America. I could maybe see that happening soon in Japan, as it's already approaching GC levels there, but it has a long ways to catch up to GC levels in America.
In a couple of months PS3 may have a hope with the holidays, but I suspect the 360 price drop will hurt the PS3 more than the Wii...