It really depends how you’ve bought your ticket.
If through *partner* FF points it’s likely EK will simply notify Aeroplan or Qantas that they have cancelled the route. You’ll then be entitled to a refund, or you’ll need to find alternative award seats. Aeroplan and Qantas have no obligation to find you other seats or rebook.
If you have *paid* cash for your seat, Emirates might rebook you on another airline. Article 9.2.2 of EK’s conditions of carriage say Emirates will select which of three options you can have if they cancel or fail to operate a flight. Option 1 is to accommodate you on another EK flight (can’t happen here), Option 2 is to re-route you on another carrier, Option 3 is a full refund.
But this is an EK choice, not the passengers’. So you might want option 2, but EK may decide option 3.
(obviously if you are booked all the way to DXB option 1 is viable, but for bookings only to SIN it won’t be)