In my opinion, the only reason why someone could claim that platforming has become stale is because so most of the developers who can produce great platforming experiences are no longer producing platformers ...
Now, there is nothing wrong with producing a Banjoo-Kazooie game that is in a different genre than platforming; in fact I think Microsoft should have been capatalizing on the Banjoo-Kazooie franchise in a similar fashion to how Nintendo uses Mario and the Mushroom Kingdom's characters in so many games. The problem is that Microsoft promised the release of a Banjoo-Kazooie Platformer and released some sort of car game; had Nintendo promised a new Mario Platformer and then demonstrated a game that was 80% Mario Kart with 20% platforming most people who were excited about the platformer would be pissed.
