AnandTech has some insight into Seagate's new 2.5" drive lineup, with sizes up to 5 TB...
The BarraCuda 2.5"/15 mm drives for external storage solutions will be used inside Seagate's own DAS devices such as the Backup Plus Portable Drive and the Expansion Portable Hard Drive products. The Seagate Backup Plus Plus Portable Drive 5 TB (STDR5000100) is due in early November and will cost around $150 - $160.