You've probably read that the wifi/ethernet sync capabilities had to be removed in ActiveSync 4.0 for security reasons. When decision was made, there was plenty of disappointment internally and a number meetings where smart folks tried to find ways to keep the feature in without risking security and without slipping the schedule commitments we had made. Unfortunately, that ended up not being possible for AS 4.0.
We think it's pretty common for developers to do debugging over wifi because debugging over USB is slower and less physically convenient. So, how does the loss of remote sync impact developers? Fortunately, not very much because we've done two things:
1) Reduce the need to debug over wifi.
- The new emulator is a real ARM emulator - it runs the same bits that actual devices do so the need to debug on real devices should be reduce all around.
- ActiveSync 4.0 supports native USB 2.0 which can make debugging over USB much much faster
2) Provide a workaround that enables debugging over wifi
- The connectivity model is Visual Studio was rewritten to support (among other things) communicating with the device without needing to go through ActiveSync. Major kudos to the Visual Studio for Devices team for pulling this off. Their instructions are here.