Don't you know, "trusted" devices means that you CANNOT trust them, because you DO NOT control them.
It's a trade off, it means that the authentication will be safe even if the operating system is compromised and in this case you would thank god for not being in control of your authentication system. OTOH you won't need to compromise the operating system if you can directly attack the hardware. Also while it's much harder to crack a hardware protection, once it's done the fix is much harder to implement.
Where things are going? A lot of security stuff already happens on hardware. VTx, VTd, TXT, smart cards... I do expect hardware to play a stronger role in security.
This is a correct move from AMD. Brings extra features to their chips without much cash outflow in the development stage. Exactly what a cash strapped company needs. As their cash situation further deteriorates, I expect them to integrate more and more IP in their chips. A security chip, a vanilla ARM core... let's see where things will go.