Thanks for all the replies.
i went to Service Ontario yesterday and inquired about the process but the person I spoke to said that I can't go there after the sale and ask them to take my name out as the registered owner. But I was not convinced, since I've read all your replies, so I emailed their support and here is the reply: (see in bold)
Hello
Thank you for taking the time to contact the Ministry of Transportation's Customer & Traveller Information Management Office.
You will need to provide the owner with the original documents:
Record your name, signature, name of buyer, date and purchase price on the "Bill of Sale".
Complete and sign the Application for Transfer. The Application for Transfer is on the back of the "vehicle portion" of the registration permit.
Keep your licence plates and the "plate portion" of the vehicle registration permit. You will need the permit if you decide to register your licence plates on another vehicle.
I would suggest that you notify the ministry that the vehicle has been sold by going to a ServiceOntario Centre.
Keep a photocopy of all the records you provided the buyer.
We thank you for your inquiry and encourage you to contact us in the future, as we continually strive to improve our service to our customers.
I have not decided on what I'm going to do at the moment but I definitely will not be going back to the same Service Ontario location.