5G will require entirely new devices and technologies
Similar to the country-wide transition from analog to digital television in 2009, 5G technology will require the development and purchase of new devices and technologies that can support it.
5G will work in a world that is mostly 4G, but 4G will not work in a world that is mostly 5G. While new 5G devices can operate on a 4G LTE network, it cannot work the other way around. Although nationwide 5G rollout will take several years, you will eventually be required to purchase a 5G-compatible phone, laptop, television, et cetera. At first, this may not seem like a huge deal, but due to the fact that this is a new and much more advanced technology, prices will be incredibly high. This is proven by Samsung's lineup of 5G-enabled smartphones; the Galaxy S10 5G phones began at $750, while the Galaxy S20 began at $1,000. Pete Lau, CEO of OnePlus - a smartphone-manufacturing company known for their products' affordability - has confirmed that their 5G would be more expensive, because 5G technology "add[s] cost". Prices will eventually go down, but while 5G is still a relatively new phenomenon, some consumers may have difficulty affording new devices. All-new devices will also lead to an increase in e-waste, due to consumers throwing away and replacing their old devices at a higher rate. Currently, only 15% of electronics are recycled responsibly. This creates concern for potential environmental consequences following a nationwide 5G rollout.
5G is more of a complement to than a replacement for 4G; it is building on top of and improving features that 4G already has. According to AT&T vice president Gordon Mansfield, "many aspects of [the old and new network] are shared", and "some things we'll do for 5G are inherently backward compatible and will lift the capabilities of 4G". It will be a long time until 4G is completely phased out, so you don't need to worry about buying a new phone yet.
Rejecting the premises