Well the third full year is normally the peak year of a console anyway.
Xbox 360 and Wii have some notable games coming out in Japan for 2009 though too so its hard to say really.
Square Enix is releasing Dragon Quest IX on DS in March 2009 so its hard for me to imagine Final Fantasy XIII coming out within six months of that time frame for me personally.
You have to figure Monster Hunter 3 on Wii will come on the holidays - either Golden Week in Spring or for Obon or Christmas. Given how Sony centric that series used to be, again its hard for me to imagine Capcom and Square Enix pitting Monster Hunter against Final Fantasy.
So based on my assumptions above, the schedule probably is like this to take advantage of holidays -
DQIX - March-Golden Week (March-May)
Monster Hunter 3 - Obon (August I think)
Final Fantasy XIII - Christmas 09' or later
PS3 will likely break the 2m barrier in 2009 in Japan though, and if everything broke right (onslaught of big games, slowing Wii momentum, little inroads for 360, price drop) as high as 3m or 3.5m.
It looks more like 2.25m in 2009 to me at the moment though, and I figure Wii and Xbox 360 can continue to see increasing sales in Japan as developers start diversifying their libraries to larger audiences.