Many years ago, when I was still puffing away assiduously, Camel cigarettes (regular non-filters) "modernized" the design of their pack at the same time that they changed the tobacco blend. Millions of people complained, and sales dropped significantly.

 

Reynolds hastily restored the old package (and secretly restored the tobacco blend), all the while maintaining that only the pack had changed, not the ingredients.

 

— Dick

 

My guess a new logo will make loyal Pepsi drinkers think, "The logo has changed, the recipe must have changed too. Am I happy about that?" (new coke) But it isn't so different that people will think it is something new and exciting. So, potentially, they will loose brand identity without gaining client curiosity.