Do you have a link to where AT&T has publicly stated such a five year plan? Because only a week ago AT&T's CEO said:
the DirecTV satellite service, which he said still produces more than $4 billion in free cash flow per year, will have a long life. But he reiterated that AT&T TV, the company’s upcoming streaming TV service, will be the primary vehicle for going to market.
So no, they are not going to "ditch satellites" and deliver all content by broadband. They will prefer to sell new customers on AT&T TV once that's fully launched because they save a lot of money on the install, but they aren't going to shut down Directv. Once installed, it isn't any cheaper to deliver to customers via streaming than it is satellite.
Roughly 2/3 of a customer's bill goes directly to networks to pay for the content, and they pay the networks the same regardless of delivery method. Most of the rest of the customer bill covers overhead like CSRs, billing, accounting etc. which is the same regardless of delivery method. Even if you could wave a magic wand and make all the ongoing cost of satellite delivery (broadcast centers etc.) go away customers would barely notice the difference if it was passed on to them as a discount on their bill.