If someone is going to eat your current business, it's better if it is you. Fear of cannibalization is basically, "our customers will find out we have an even better product for them than the one they are currently buying from us." It's a good thing for your customers, and it's good for the long-term competitiveness of your company.
I've always told my business partners when discussing future products that if you aren't afraid to cannibalize your own revenue streams, your competitor (or another internal team) will.
