Other than bloggers and journalists and tech types, I'm willing to "bet" in 2019 the average joe is not going to care about 5G especially if cell phone plans in the US undergo no change. At some point public perception will catch up to those models that don't have 5g chips, but not in 2019.There is going to be a huge buzz in the media all carriers around 5G all year long. 5G is going to be the new buzz word around mobile internet access and home internet access too. Apple will have a PR problem and give people less of a reason to upgrade if the 2019 iPhones do not have 5G.
Just having a better camera will not be enough of a reason to upgrade at the prices Apple is charging. They are already seeing a slow down in sales.
Public perception (right or wrong) will be that iPhones are behind in current technology if they do not have 5G.....
For example I live in an area with marginal signal quality. 5G is not going help me and I can almost guarantee there will not be any new towers in my area, even if they are micro-towers.