Actually, it's only TA's who don't book through Walt Disney Travel Company directly who cannot apply a discount code if one comes out.
Chances are any 'regular' TA (i.e. Marlin Travel, Sears, Carlson Wagonlit etc) will book through a Canadian Tour Operator such as Air Transat, Nolitours, Air Canada Vacations etc. However, a Disney Vacation Specialist knows to book through Walt Disney Travel Company directly, as that way you can apply any discounts.
Side note - it's the Canadian tour operator who doesn't allow you to change the price, not Disney. Disney will allow the tour operator to change the pricing AFTER discounts come out, it's the tour operators choice not too, as they don't want to give back money after they have it.
I suggest booking with a Disney Vacation Specialist. And to book now, as you can begin making dining reservations as of now for May!