Windows Phone 8 will come will come with many new features and improvements such as multi-core support, Skype integration, Cloud service improvement, HD display support, and others. Unfortunately, current WP 7 devices will not get update to WP 8. They will be updated to Windows Phone 7.8.
Windows Phone 7.8 has some new features on WP 8, like variable tile size, removal of the gutter, and new tile colors. But, there are many features not included in WP 7.8. The table below gives you comparison between Windows Phone 7.8 and Windows Phone 8.
|Functionallity||Windows Phone 7.8||Windows Phone 8|
|Bing Audio||Yes||Yes, with improved recognition TV|
|Browser||Internet Explorer 9||Internet Explorer 10|
|Cloud||Office OneNote, 356||Synchronization of all content|
|OTA||No, only notify||Yes|
|Updated startup screen||Yes||Yes|
|Visual Voicemail||Only for some countries||Yes|
|Voice commands||Yes||Yes, extended set|
As you can see on the table, Windows Phone 8 is much better than Windows Phone 7.8. It comes with IE 10, while WP 7.8 comes with IE 9. Over the air update is supported on WP 8. It also offers better cloud synchronization, DataSmart, RSC-e integration, and Skype integration.