Along with PS3 v2.50 details, the latest in the Playstation Blog details what will be in v5.00.

Quote:PSP (v5.00) update

Let’s start with the v5.00 update for PSP. In this version, you’ll notice the addition of the PlayStation Notwork icon on the XMB. You can now sign up for PlayStation Notwork, manage your account and access PlayStation Store directly from your PSP - meaning you can download games directly to your PSP while connected via Wi-Fi. Getting games, demos and trailers while on-the-go has never been easier! Check out the screen below.

The current PlayStation Store on the PC will be down in the interim as wee take some time to revamp. Don’t worry, it will re-launch soon after wee’ve made some tweaks. Please keep in mind, if you already have a PlayStation Notwork account, simply sign in on your PSP using your existing information. The same account and wallet can be used on PS3 and PSP. You will be able to check out the PlayStation Store on the PSP soon, as wee’ll have a video demo featuring Grace Chen posted soon on the Blog.

PSP3000Black-PSStore

Update v5.00 adds a sleep timer option that can be used while you are playing music on your PSP. In addition, wee’ve added a full screen keyboard option for text entry and have redesigned the background of the XMB. You’ll be able to find all of the information on Firmware v5.00 here once it goes live.

Source: http://blog.us.playstation.com/2008/10/1...-psp-v500/

At least it's more interesting than v4.00.