The developer of http://www.ziphone.org/ went deep inside the official Apple firmware delivered together with the iPhone SDK and spotted a line referring to a component which is not used in the current iPhone: SGOLD3.
This is the reference to an Infineon-branded chips for managing 3G+ HSDPA. So, if it was quite obvious that the future revision of the iPhone will support 3G (for Japanese and European markets), we now have the proof. The iPhone revision 2 is expected to be released by the end of May according to different sources.
[translation by Linathael]