"Halo 4: I Get a Woman!" - Sgt. Mjr. A.J. Johnson, RIP

[Kornman00]

Jen stayed with Bungie as I recall.
I think the explicit avoidance of saying whether Jen would voice Cortana was a sign that Jen won't be involved.

Voice actors tend to not have any particular loyalty to a company though. I seriously doubt she wouldn't voice Cortana.

Just came across the following post on HBO which suggests (and has backing support) Jen won't be the babe behind Cortana's voice and facials...