First, if you look at CERDEC US Army website, http://www.cerdec.army.mil/ the last news they posted was in July. So does that mean they haven't signed any contracts since then, I don't think so.
Also, why would CERDEC announce this. This is an investment to them at this stage. If Arista follows through and delivers a great product, the next step will probably be another contract for the purchase of some units for testing. Then, if the product tests well, we will probably see a contract for the purchase of X numbers of units. That is when CERDEC will announce this.