Of course the BREAKING NEWS of the day was...
No WP8 upgrade for existing WP7.5 Lumia phones, instead they will get WP7.8
Microsoft also announced that the Windows Phone 8 will NOT be available in its entirety for existing WP7.5 devices (the Lumia 610 710 800 and 900) but these devices will get some of its the features.
In an upgrade conveniently called WP7.8 (7 to 8). WP8 features that do NOT depend on their hardware will be available for existing WP7 phones, hence they will get the new start screen, multi-tasking, internet explorer 10, integrated Skype, new maps.
However, the existing Lumia will NOT get hardware specific features... NFC, wallet, microSD, dual-core CPUs and this is for obvious reasons..
Here's a nice demo of the WP7.8 upgrade running on a Lumia 900, it shows off the new Startscreen.