Here is an article that generalizes all the things we have now (in Windows Mobile 6.x.x) and won't have at the launch of the new Windows Phone 7.
The main things are native code support, database support, access to data on SD cards (yes, that's right, some of the Windows Phone 7 devices will have SD card, but since Silverlight applications can access only isolated storage, they won't be able to access the data on them) and socket support (that's why applications like Skype can't be made for Windows Phone 7 for now).
Notice that in this article it is said that Windows Phone 7 won't support video capturing, but from Microsoft disproved this information and posted a video made by the WP7 device. Notice the video and the sound quality!