although you need to sign another 3 years, which means you extend 2 more years, you can upgrade at the 2nd year from this upgrade.
you can upgrade every 2 years at the same price as a new signed user. so do waste the time until your contract expire if you have no plan to leave canada.
and family plan is not better off than a free Rogers to Rogers R2R feature.
I think it's better to negotiate your plan first and then upgrade. because Rogers will consider Iphone4 as a favor.