Sony released the Sony PSP firmware 2.81 in Japan. You only need this new firmware if you use Sony Memory Sticks with capacity greater than 4GB.

Sony announced the 8GB Sony Memory Stick Pro Duo early this year to be available in 2006, but I can not find it on any store yet. The highest capacity available is still just the 4GB stick.
The firmware release can then be taken as an indication that the 8GB Memory Stick will soon be available. At least in Japan.
To have 8GB inside your Sony PSP is nice and gives enough space for music and videos on the go.
Details about the new Sony PSP firmware update can be found here (Japanese). The download is here (Japanese).