Tom Brokaw has served the media for longer than most of America has even been drawing breath. He has been the voice of both tragedy and triumph. The American people will of course rally to support him in his time of weakness. Cancer is an affliction that has touched every family, regardless of stature. It is a universal tragedy that no one escapes from. He may realize some personal gain in the form of sympathetic gestures. However, he is also raising money for research, even if it serves him, the research funded for cancer in his name is just as universal as the disease itself.
Yes, I think Tom Brokaw will enjoy a lot of support from fans and admirers. As a successful and accomplished figure, a lot of people will want to see him get through this. I'm sure he'll get a lot of encouragement. Moreover, I think that getting it out in the open will make the cancer itself seem less formidable.
Financial gain? No, probably not. I would think that someone like Tom Brokaw wouldn't feel the need to benefit financially from having cancer as he probably has enough money as it is. He might benefit mentally and emotionally from listening to the stories of other cancer survivors and sharing his stories and experiences with them.
I doubt Tom Brokaw will realize any real personal gain from announcing his cancer. Of course he will now identify with a new segment of the population, those that have lived through cancer or are currently battling it. He may have the opportunity to write about his experiences or share his experiences, but overall I don't think it will be for personal gain.
Any celebrity who announces their cancer is probably not doing it for personal gain, other than the fact that they get a lot of support from people. What they are doing is personalizing the face of cancer or some other disease so that the general public feels more comfortable talking about it.