The 20GB, 40GB and 60GB versions of the PS3 have been discontinued. According to this, the 80GB PLAYSTATION 3 looks like its next.
This notice is apparently from retailer 7-Eleven (7-Eleven sells video games in Japan) and stats that pre-orders for the Black, White and Silver 80GB PS3 will cease on Sunday, August 9 at 10am.
The reason listed for this is "For the manufacturer".
The notice also notes that all in-store displays for the 80GB model are to be taken down. If this is true, then Japan would be left with only the 160GB PLAYSTATION... Or perhaps there is an upgrade in store...