Microsoft in a Windows Phone Developer Summit are just showing bit by bit about Windows Phone 8.
Main new features are as below:-
Windows Phone 8 will support Multi Core (up to 64)
It will support HD resolutions 800 x 480 display (they can opt for more.)
Now Windows Phone will Support SD card which was awaited for long.
Windows Phone 8 will support NFC and will also support NFC payments.Also Support for payments with cards.
Windows Phone 8 will have Internet Explorer 10 which will be pretty similar to the Desktop Version.
Windows Phone 8 will also have Nokia Maps support.That means you don't have to own lumia phones for experiencing the Nokia Maps,Microsoft just confirmed that Nokia's map is being built into Windows Phone 8.(Along with offline navigation and many other Nokia Drive goodies)
Windows Pone 8 and Windows 8 for PCs shares alot of things and Also now developers can port their apps to Phone, To Tablet, and the Desktop as well. Full fledged NT kernel for coherent ecosystem
Still many things are to be revealed. Stay TUned!!
*Update 1) Older Phones with WP7.5 will not get long awaited update of wp8.But they announced that it will get an update version 7.8 with some software goodies from wp8 (SOURCE- Endgadget) (Nothing Debated about Lumia Series Yet)
*Update 2) WP8 will now support In app purchase!!(SOURCE- Endgadget)