Verizon no doubt will refarm the spectrum to expand its LTE footprint. Other carriers are closing down outdated technology such as the iDEN pipeline that Sprint is closing down next year, and by 2017 AT&T will shutter its 2G GSM network. The last of the analog networks already disappeared in 2008. With spectrum scarce and LTE coverage beckoning, carriers need to eliminate rarely used spectrum and refarm it to expand its LTE coverage.
By the end of next year, Verizon's LTE service will cover its entire 3G footprint and the carrier will introduce VoLTE in 2013. Currently, calls made by Verizon customers are routed over the CDMA pipeline but Big Red will eventually have voice and data carried over its LTE network.
UPDATE: So it turns out that a "decade worth of pre-warning" does not necessarily indicate that Verzion's 2G and 3G service will be around for exactly another 10 years. Here is an official comment on the matter: "The Verizon Wireless 2G and 3G networks will be available into the foreseeable future. Recently published dates are guidelines that we are giving customers who have to plan, fund, and transition large enterprise projects to the faster speed networks. The Verizon Wireless 2G and 3G networks will be available as long as necessary to support customers who may have mission critical projects on those networks."