IGN has a preview on Halo 4  showing the NEW Legendary Shield. They (343) state that it’s Forerunner in origin.

Okay, so do you like this new shield and skull?

I like it. It of course HAS to change from being Elite to something Forerunner as the Forerunners (or at least the Prometheans and presumably the Didact) are the main enemy of Halo 4, not the Covenant.

Thanks to HaloWaypoint for the link. Screencap of shield by VaderRx.

Here’s the shield recolorized and cropped a bit.

-Sal