Eric Lempel, over at the PlayStation.Blog has confirmed that PSP Firmware 5.00 will be released soon. Lempel also confirmes that Firmware v5.00 will include PlayStation Store support, adding a new menu to the XMB. The PlayStation Store will allow users to download games directly to their PSPs instead of using a PC or PS3. You will be able to use your existing PlayStation Network login (whether PC or PS3) and you will be able to manage your account directly on the PSP.
With the PlayStation Store coming to the PSP, the PC PlayStation Store will be down for a while to revamp the store. You can use your existing PlayStation Wallets to purchase items from the store too. A video demo of the store will be released by Sony soon. In other changes, a sleep times has been added to the music player and a full screen keyboard option has been added. The XMB background has also been redesigned.
More details on the new features will be available once the firmware update goes live.