Some people say that the VOs will be busy for processing the study permit since May. So the March AORs will have high chance to be delayed if PPR is not received by May.
https://myimmitracker.com/en/ca/trackers/march-2018-aor-permanent-residency-tracker
Look at this tracker. There are already 10 March AORs got the PPR. Let us hope for good.