The iphone 4 will not do 4G. Most likely in the 5 or 6. My bet is on 6 since most cell providers are not fully upgraded to do 4g. They are partially upgraded but not 100% yet.
It all depends. It is defferent tech. Like how people used to only have dial up then here comes DSL and Cable. And now comes Fiber-optic. Yes some of those existed back in dial-up days but now it is affordable to the public.