The GTI is only seen as a 2007 in Canada. The place you should worry about it being a 2007 is your registration with the provincial government. If your insurer is quoting you with 2006 rates, ask for something in writing that indicates they are aware that you own a 2007. That way if there is any confusion down the road they can't say that you misrepresented the car you owned.
As far as it being registered as a 2007, if your dealer registers it as such, that's what it is. The paperwork they present to the registrar (the nivis form) already has the year on it, unless they totally screw up and enter the wrong numbers, you shouldn't have any problems.