It will apparently be announced at E3 but won't be shown on the floor. The rights have returned to Stainless, but don't seem to be behind the development.
Someone else is handling the new Carmageddon title on their behalf. Stainless made the 1998 sequel Carmageddon II: Carpocalypse Now, while a third was made in 2000 by Torus Games called Carmageddon TDR 2000. All three were multiplatform releases.
Magic: The Gathering and Risk are being tapped by Stainless who create digital downloadable titles for the two franchises. It seems they're passing the torch to another outfit for Carmageddon's return to hopeful glory.