One thing I noticed when doing my unboxing video, is that the 521 did not have any connectors integrated into the phone for a wireless charging back. If you notice the back of the 710, you see 3 metal circles. Those are to connect to the battery for the charger. The only connectors I see are for the battery itself. It is possible that the wireless back can connect onto those, but its just not engineered that way. Has it been confirmed that the 521 will have the option of a wireless charging back plate?