They won't - their most valuable assets are their spectrum, and broadcasting free content on them is a requirement for owning them. They're looking to reap billions when they "sell" the spectrum back to the FCC in the upcoming wireless incentive auction. (I use "sell" in quotes since they never really bought them and in theory, the airwaves are owned by the government).
They do not own most of those assets directly, only a small fraction of their local affiliates are actually owned by CBS. Additionally, they are not mandated to broadcast their main money-making content on that spectrum either -- they could provide 24x7 wheel of fortune re-runs and a simple re-broadcast of the local morning and evening news would probably be sufficient for them to maintain the license.
