I think they're buildout dates on AWS-4 are already on the clock and will expire in 2015, I think?
Also, while a minor point, Verizon, to my knowledge, does not own any WCS. They do own truckloads of AWS and will likely use all of it they get their hands on (assuming it's in the right areas). Considering AT&T has already started to use their PCS for LTE it's only a matter of time before WCS gets it's time. However, AT&T's AWS is a little more tricky. I believe that they are using AWS LTE in OKC or somewhere around there (AJ knows) and I suspect that they are using AWS LTE in my town of Lincoln, NE, but that is unconfirmed.
EDIT: my AWS-4 buildout date is completely wrong, please ignore it.