I have to say I didn't see this one coming from a Microsoft employee blog – you guys are stealing our posts! ;-)
"Windows Live ID will replace the Microsoft Passport service. Windows Live ID will be the authentication system for Windows Live, Office Live, Xbox Live, MSN and other Microsoft online services. Partners who have implemented Passport are compatible with Windows Live ID.As with all platform releases, our next release is not just a branding change for the service. There is a significant amount of work that we've done to not only help partners and end-users realize more scenarios, but also to increase availability, performance and pave the way for future scenarios by making investments up front.This moves reflects our intense focus to support the new sets of Windows Live services that have been, and will be launching, in full force (eg. www, expo, domains, mail to name a few that have already shipped). As previously mentioned, Infocard support will also be added as a supported credential type."
As Trevin mentions, Windows Live ID will be compatiable with all Passport sites and will add support for using Infocard as a credential. In fact Trevin addressed this issue previously in his blog post Official word on Infocard and Passport.
The change to Windows Live ID will mean several changes for users, most obviously with the new signin pages they will experience as well as an overhauled accounts management site. You can see the new login screenshots linked below. We've heard that the standard buddy picture will actually use the local display picture of the user signing in (if available) but we have not been able to confirm this ourselves yet.
For those who don't know, Trevin Chow works on the Windows Live Identity Services team.