Very well, there are several arguments from which you prune to arm a serious proposal to the managers and the shareholders (it goes with links for more information).
First of all, it is the life cycle of the product (http://es.wi kipedia.org/wiki/Ciclo_de_vida_del_producto). Sooner or later the product dies, since he behaves like a living being. If the company only survives with that one, this one destined to die with. It is very common that when the companies obtain the "dairy cow" (according to the counterfoil of Boston Consulting Group: http://apuntesalmargen.com/mar keting/matriz-del-boston-consulting-group/) stop looking or investigating on other products that accompany it while they study for other stages of the cycle. The motto is "if the things worked so till now, so they must remain". Nowadays, cualquer organization considers the establishment of an area of research and development (http://es.wi kipedia.org/wiki/Investigaci%C3%B3n_y_desarrollo) in some moment of his growth.
Another argument is that the movement of the market is needed preveer and to make use of the business opportunities as well as to generate risk mechanisms for possible threats. The passive management instead of the proactive one, leaves the most vulnerable companies before a crisis and much more before the effective competition.
Also prune to base from the stock point of view. Every participant of the income of a company not only wants to maximize them, but to make sure that the company is doing all the possible to increase them. If you leave well in clear that not only it is not maximized but it is "stagnating", insurance they are going to ask you please to show them the way of being able to go out of this situation. Others related can be interested in this inclusive with the company like the same personnel, the managers and, inclusive, the same clients (http://www.eumed.net/tesis/2006/flsp/5s.htm) Of course, tenes that to be sure well, know well these arguments and others that you could go so far as to find and present all of them in a tidy and coherent way. Tenes that, to be ready to defend the idea and that needs to be well planted.
I you hope to have been helpful and luck with that!