Note there is a difference between getting citizenship and getting passport. Refer:
https://www.blsindia-canada.com/renunciation_ppt.php
If one gets a Canadian passport then the grace period does not apply. Under this circumstance you need to apply for Indian eVisa.
However post the Oath, if you don't get a Canadian passport you can travel to India on the Indian passport but later cannot get into Canada since your PR card is taken. This is a catch 22 situation.
I think the options would be
1. to postpone the oath to avoid the situation or
2. get the Canadian Passport and apply for Indian visa.
3. If you have time get the Canadian Passport then surrender Indian one. Finally get an OCI. But for this you should provision about 1.5-2 mts.