> mmWave is a dying tech. It will suffer the same fate as WiMAX. If this is the trade off (and it shouldn't be), I'll choose the SIM slot every time.
I think mmWave has a lot more staying power than WiMAX. WiMAX as deployed was an alternative network to general purpose cell phone networks. As a third alternative to CDMA/GSM and upcoming LTE, it didn't make a lot of sense in the market.
mmWave is deployed as augmentation to a network, mostly to increase capacity at hotspots like stadiums and maybe transit centers. Additionally it provides beneficial marketting, because network providers and handset makers can claim their network/device does huge bandwidth even if it's only true when you're the only person in a stadium.
Given that US iPhone 12 and up support mmWave, and that spectrum management is a challenge at stadiums, it's pretty likely we'll continue to see deployments in that space. Even if mmWave doesn't live up to the marketting, moving half the customers to it frees up traditional spectrum for those customers that don't have it.
Is it going to expand much beyond those situations? Maybe to airports and NYC train stations, but probably not beyond that. Is it ever going to be more than a small fraction of time connected for people other than stadium employees? No. Does that mean it's dying? No, it's just a constrained niche. Should you prefer a phone with or without mmWave? Depends on how often you go into situations with high person density.
