This week, the telecom giant provided more details about its plans for the 5G home service, which is likely to compete head on with cable giants like Comcast, Charter Communications (CHTR) and Altice (ATUS). Just how quickly that desperately needed competition will arrive, however, is an open question.

All the major wireless carriers are experimenting with 5G, which could offer mobile speeds 10 to 40 times faster than today’s 4G LTE networks. AT&T (T) has also been experimenting with a wireless home Internet service, while T-Mobile (TMUS) has been focusing on testing faster access for mobile devices.

Meanwhile, Verizon may be the furthest along having already paid billions of dollars to get access to 5G-capable airwave licenses from XO Communications and Straight Path Communications (STRP).

At a closed-door meeting on Wednesday, Verizon told Wall Street analysts that it plans to start small, with just five cities in 2018, but that it is ultimately targeting 25% to 30% of all broadband households, or about 30 million homes. Sacramento will be first city, but Verizon didn’t disclose its other four initial markets. The nationwide goal means Verizon will be expanding well beyond the largely northeastern footprint of its current Fios wired home Internet, TV, and phone offering.

Early trials this year with the 5G system, which uses much higher-frequency airwave bands than today’s mobile networks, have shown even more positive results than the company expected, Verizon’s new chief technology officer (and former CEO of Ericsson) Hans Vestberg told the analysts. The new home-oriented service would be a so-called triple play, offering gigabit-speed Internet, a cable TV-like channel bundle, and voice telephone service at a “competitive” but “premium” price, head of wireless John Stratton said according to analysts who attended the meeting.

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But Verizon was cagey when it came to details about the rollout beyond the initial five cities, and said it couldn’t estimate the cost of building out the service nationwide until late next year. To the analysts, that signaled that Verizon was going to see just how successful it could be in the first five cities before truly committing to go national.

While the 5G technology is supposed to provide a cheaper way to connect homes than older, wired broadband networks, the industry still remembers Google’s claims that its high-speed Fiber service would undercut cable, which did not prove to be the case. Lately, the Fiber unit has stopped expanding to new cities, laid off staff and run through several CEOs.

“Google Fiber was here once upon a time, and much more was known about the cost of deployment and the capabilities of the network…and it still died,” noted analyst Jonathan Chaplin, at New Street Research. “It looks like we won’t know how committed Verizon is to this or how much of a threat it will be until this time next year. Until then we remain skeptical.”

Morgan Stanley analyst Simon Flannery also picked up on the possibility of a slow deployment, with local government cooperation another key variable. “Future market rollouts will depend in part on negotiations with cities and early commercial results,” Flannery concluded.

Craig Moffett, at MoffettNathanson Research, said: “The way all this plays out is so murky as to be unforecastable. The most likely outcome is, of course, incrementalism.”

The bottom line, at least as far as Wall Street is concerned, is that Comcast (CMCSA) and its peers probably don’t have much to worry about from Verizon (VZ) at this point, says John Hodulik at UBS. Wednesday’s announcement “suggests the impact to cable will be very small and potentially imperceptible in 2018 and longer-term would depend on the viability of the business plan,” he noted.