I never have problems with 4G speed for what i need (browsing, google maps etc.). i don't stream Netflix etc. outside my wifi area, so can't tell if 4G suffices for that. i seem to be able to use youtube on 4G properly, though.
My main problem with speed is that most rural areas don't even have 4G and google maps (if I didn't download a map before) becomes unusable at what I perceive as dial up speed. since 5G has a shorter range, it won't resolve that problem. 5G first will have good coverage where 4g is already dense.
it will be a long time before 5G goes into rural areas, if ever. I assume wherever there is 5G, there will be 4G, or a 4G phone can use 5g at least at 4G speeds? anyway, it won't be an issue for years to come. I believe my 4G phone also uses 3G (in rural areas it says so)