On topic: I recently replayed all Banjo games on my X360 (and GBA emu) and I can still say: These are some of the best games I ever played (my favorite genre is '3D-Platformer-Collectathon', hense my opinion) and I really can't wait for Yooka-Laylee to be released! (L)
Considering the number of times I've replayed both Banjo and Tooie for the game design alone, no. I wouldn't say it was only out of nostalgia. In fact I'd say a lot of games today are lacking in many ways, and are more prone to tedium and unoriginality. No beloved genre should ever die off for fear of trying, and nostalgia is a valid means of enjoyment either way.