Saturday, January 5th. If NH goes on Jan. 8th, IA will simply change their law so that they don't have to go 8 days before NH. They really don't want to do it in 2007 or on New Year's Day.
Also, it's not true that NH will go later than Jan. 8th. It's not a sure thing that MI will go on Jan. 15th. If they don't, then NH could go as late as Saturday, Jan. 12th. But either way, I predict Iowa on Jan. 5th.
There is no law that Iowa must be 8 days before New Hampshire; it's become a tradition, but unlike New Hampshire, there is no law about it.