Wikipedia says "Intel 64" is the new official name, but yeah, IA-64 looks wrong. Sorry. IA-64 feels like it should be the 64-bit-ified IA-32, but no...
You're actually right...IA-64 was suppose to be the 64-bit Intel instruction set, right up until AMD dropped the AMD64 bomb and the market went "backward compatible...got to get me some of that" and Intel went scrambling for Plan B.