Please remember to use WikiFormatting, to fill in the Port field, and to Cc the maintainer of that port.
Yes, it appears qt4-mac has been stealth-updated by its developers. The distfile we mirrored at the beginning of the month, for which the checksums in the portfile were written, is 219424772 bytes, but the file available on their servers now is 220388303 bytes. The diff between the contents of the two distfiles is enormous, about 1.8 million lines long, all in the doc directory, mostly the html files. qt4-mac does install html files; if these changed html files are the ones that the port ends up installing, the port's revision should increase when it follows this update.