Stuff like BGAN only does around 400kb/s. Even modern platforms such as "SPACEWAY" only get up to 30Mbps.
Believe me, it's going to be a looooong time before you see 400Mbps coming from a satellite
This is an operator's choice with respect to its business case, not a technical limitation by the satellite.
The bird carries 30-40 transponders (Ku band), each has a bandwidth of about 50MHz.
A 50MHz pipe, with compression, can deliver very high speeds....but there is price to pay.
BGAN tops at 512kbps (IP mode).