He knows.
First of all, the doctors have already talked to them about what this means. And second, he didn't become a highly-successful trial attorney by being an ignorant fool. It's pretty common knowledge that when breast cancer spreads to the bone, it's going to be fatal.
I imagine they'll conduct additional tests to see if it has spread to other organs.
John knows all this, and he used today's event to get huge publicity, sympathy, and campaign donations.
If he dropped out now, he'd be a nobody in four or eight years when he could run again.
I now hold him in lower esteem than I even thought possible. If we find out that his campaign leaked the false story of suspending the campaign in order to make the press conference even more dramatic, I doubt I could contain my outrage.
I am afraid I have to agree with you, Dog Gone.