As the third quarter draws to a close, at least one cable TV analyst is optimistic about a key element of the business. Major cable TV operators will add 6% more subscribers to high-speed Internet service in the third quarter than they added in the third quarter of last year, estimates Smith Barney analyst Niraj Gupta. And though telephone company price cuts have pushed adoption of the DSL service that competes with cable modems, the increasing popularity of DSL doesn't appear to have come at the expense of cable operators, including Comcast (CMCSA:Nasdaq - commentary - research), Cox (COX:NYSE -...