I do not think that it will be able to get full 4G because in the videos and blogs where they tear the phone apart to see all the inner pieces they never mentioned anything about a 4G able radio. I do think it is possible for something like up-conversion though. I guess similar to the idea of dvd's and blue rays. There are dvd players that if used on an HD tv with the correct connections (hdmi chord or component chord) that can give better definition to a movie that is on a standard DVD.
So could the 3g potentially be a littler faster, if given a better/stronger signal, it is possible.