They are bringing some features from WP8 to current devices (at least it seems so), like the new start screen, etc.
So besides support for NFC, dual core, new resolutions - it appears that most of the software based updates are coming to current devices in the form of WP 7.8
It's extremely unlikely, if it was the case WP7 devices would have just gotten WP8.
The opposite is possible because if Microsoft just immediately trashed all the work their far and few WP7 supporters have been doing to help the platform, literally nobody would be on their side at that point.
You can only throw out the drawing board so many times before people lose any trust that you will ever settle on something for any real length of time.
So besides support for NFC, dual core, new resolutions - it appears that most of the software based updates are coming to current devices in the form of WP 7.8
http://www.theverge.com/2012/6/20/3096945/windows-phone-7-8-...