So what do you guys think?
Here is my answer:
Not exactly. I consider Rhythm of the Pride Lands as part of the canon, but not as a separate entity. What I really consider the CD as is a part of the original movie. This is why I never rate He Lives in You as my favorite song in Simba's Pride - because it was made for the RotPL, and therefore belongs to The Lion King and not SP.
Many of the songs in the CD are already in The Lion King in one form or another, Hakuna Matata and The Lion Sleeps Tonight being the most obvious. But the other songs, such as Lala (when Simba misses Mufasa), Lea Halalela (Nala's escape form the Pride Lands), Warthog Rhapsody (another Hakuna Matata version), Busa (Simba's ascension to the throne, and for that matter, his theme) - all these songs have a place in the movie.
Some of the other songs don't have an obvious location for where they belong, but can still fit. Kube can be also connected to the Hakuna Matata lifestyle (if only by its upbeat nature). It's Time, Noyana, and One by One can be songs that are simply sung throught the African lands by the animals living there. And Noyana is already a traditional African song...
So yes, all of the songs have a place in The Lion King, and are therefore canon, at least in my opinion.