Size matters here! So far these larger HD's need a bit more head room. Your AirPort space is limited to a 26.1mm height drive.
As for these new drives so far we have been teased with there intro. In the case of the Seagate drive offering you can't buy it as a bare drive only as part of an external drive via LaCie.
Remember these are NAS drives not desktop class drives (read - slower RPM on many & slower read/write).