The telecom had initially aimed to bring three to five cities online as part of its initial rollout. McAdam said his company has "locked in" four so far.

This won't be the most aggressive deployment in some respects -- AT&T has vowed to launch mobile 5G in a dozen cities so far, and has named three of those cities. Practically speaking, though, none of the carriers are likely to have the service you're expecting until 2019. Many early 5G-equipped phones and tablets won't ship until 2019, and smaller carriers like T-Mobile and Sprint won't even switch on their networks until the same year. As with AT&T, this is more about shouting "first!" than anything else.