Google Fiber will give cable and Internet services a run for their money because it is a faster connection than normal. When there are plenty of livestreaming options that have nothing to do with television, the new technology will surpass the download speeds of current Internet services. If cable and Internet companies don't hustle, they'll be out of business very soon.
Many of the cable companies in our country have been afforded the possibility to operate without competition. Other Internet providers, generally offering lower class Internet services like DSL and dial-up have been pushed out by cable Internet. I think it is fair to say that Google Fiber is a serious threat to both Cable and Internet companies.
The internet speed available to the customer is dictated by the equipment in the cable head end. Most cable companies have equipment that is equivalent to what Google Fiber is using. Most cable companies could give their customers incredibly high internet speeds but there is no logical reason to. When Google Fiber arrives, the other cable companies can throttle up their speeds to match Google's. Most customers will be thwarted by the $300 installation cost that Google is offering. The cost of building infrastructure is enormous and other cable companies have their's laid out.
Cable companies already have the technology to offer 1GBPS speed with their existing infrastructure. For them to offer a product that compete with Google would be easy. It would be foolhardy for Google to come in and build out a national infrastructure. Google Fiber in its current form is a PR tool, and nothing more. In the event that Google Fiber decides to roll out nationally, the cable companies would roll out faster packages and destroy Google's return on invested capital.