The Japanese aren't great fans of GTA, although San Andreas got pretty respectable sales (bearing in mind, of course, that the number of PS2's then was at least four times those in use now). Of course, when you look at the fact that San Andreas is the best selling game of the last two generations, you see what a small percentage of the sales were found in Japan. I say an optimistic first week for GTA4 in Japan would be 100k.
LBP is a wildcard. Yes, it's a western game, but I think it can go over well- that kind of deceptively casual thing seems to go over well in Japan. It's safe to assume 150k.
Of course, GTA4 is not a PS3 exclusive in Japan (is it?) so that won't be much of a bump, but I still say 20k would be a reasonable sales figure for the PS3.
(Former) Lead Moderator and (Eternal) VGC Detective 
