OK guys, Citrix has launched Presentation Server 4.5. However, it is not available for download yet.
Brian Madden has an excellent article on his blog. It looks like Citrix will drop the Standard Edition and will launch a new version called "Presentation Server Platinum Edition" (what's in the name).
A remarkable thing is that it will support 500 users per server (!). This would need a powerful server + an x64 edition on it for sure.