I don't disagree with what others have put above but the only serious problem is if you wish to keep your PR status and/or cannot travel by air:
-if you get to a port of entry (eg arrive by land) and show your expired PR card you will be admitted (as in they must admit you).
-at that point, the CBSA officer will either issue the report above or ... won't. It's possible they will just wave you through, and possibly suggest you renounce your PR status to be able to visit in future.
-Since the worst consequence is that you spend a bit longer at the border and - in due course - have your PR status revoked, it's basically not a problem IF you're okay with losing the pR status.
-If you do renounce before coming to Canada, you'll have to wait until that process is complete (a couple of months?) before applying for a visitor's visa (if you need one) or similar (ETA if you need one).