I started digging around and came up with some information on what Chevy's got for the 2013 Silverado. From what I've been told these aren't going to hit the dealer lots for a few month weeks/months, but I'm chomping at the bit to see what they've got in store. Here's what I was able to pull together from the RPO codes alone.

Silverado 1500

Deletions
(37U) Imperial Blue Metallic
(58U) Black Granite Metallic
(QXN) Tires, P265/65R18 on-/off-road, blackwall
(PEF) Florida Edition (Residency-based package)
(VMK) LPO, Cargo Management System Rails
(VML) LPO, Sliding bed divider
(VMM) LPO, Overhead rack/bed divider
(VZV) LPO, Overhead Utility Rack
(VPD) LPO, Deluxe Chrome Package


New Features
(66U) Deep Ruby Metallic
(98U) White Diamond Tricoat
(GTS) Blue Topaz Metallic
(RBX) Tires, P265/65R18 SL 1112T all-terrain, blackwall


Changes
(CF5) Sunroof, power (No longer available on Silverado Extended Cab models)
(NQH) Transfer case, electronic Autotrac with rotary dial controls (available on 1WT & 1LS)
Silverado 1500 Hybrid


Deletions
(37U) Imperial Blue Metallic
(58U) Black Granite Metallic


New Features
(66U) Deep Ruby Metallic
(98U) White Diamond Tricoat
(GTS) Blue Topaz Metallic