One of Colt's people at Media Day told me that the Colt SCW (Sub Compact Weapon), or at least the short buffer tube and foldable stock, will be coming to a semi-automatic civilian legal rifle.
Colt SCW at Media Day. © Bryan William Jones
The full auto version was on display at SHOT and I had the opportunity to shoot it. Lots of fun 
No more information on this compact carbine is available other that what I have already posted, but here is a photo taken at SHOT by Remov:

Click to expand. Photo Copyright Remigiusz Wilk (REMOV). Used with permission.

Click to expand. Photo Copyright Ken Lunde. Used with permission.
Murdoc has more photos here and here.
Over the past few months Colt has been unveiling a variety of new AR-15 firearms. If a replacement for the M16 or M4 is chosen they want it to be a Colt. To ensure this designed a range of weapons that should cover all bases. David @ Defense Review has been relentlessly covering the new firearms.
Many of the improvements Colt have developed have been applied to all these guns, I won’t list them all, click the links to read the full details.
Colt Sub-Compact Weapon (SCW)
A 5.56mm 10.3″ barreled sub-carbine/PDW featuring the new Colt side-folding stock. It is able to use an upgraded gas impingement system or the Colt Piston System (CPS)

Side Folding Stock. Photo by SMGLee.
Colt ACC-M (Advanced Colt Carbine-Monolithic)
This is basically an upgraded M4. It features many small improvements over the M4A1 and Colt’s new monolithic rail system. If it was adopted it I think it would probably be named the M4A2.
Colt Advanced Piston Carbine (APC)
David calls this the HK416 killer. It utilizes the Colt Articulating-Link Piston (ALP) system.
Colt Advanced Hybrid Carbine (AHC)
This carbine features a hybrid gas impingement and gas piston system. I am very interested to see how that works.
Colt Infantry Automatic Rifle (IAR)
I covered this a few weeks ago on the blog. It is a light machine gun and Colt’s entry into the Marine Infantry Automatic Rifle competition.

Colt IAR. Photo by SMGLee