Hi,
very unlikely but rejection can still happen at any stage before you finish your landing.
for example if you commit a crime or have a criminal background check or made a misrepresentation during your application and these information come to the line you will be rejected even though the visa and confirmation of permanent residence has been issued,you can still be rejected at the port of entry when you try to land.
if you have nothing to worry about then you are cool,just chill and its only a matter of days until you become a permanent resident of canada.
good luck.