No we don't know the answer. The doctors do have an informed guess that they are not sharing. Actually, nothing but platitudes are being shared.
We know the answer because they aren't saying. If they say anything, guys like you would have an informed opinion that you'd share with the public. If the prognosis were good, we'd be inundated with information about Senator Johnson's courageous fight. So we may conclude that the prognosis is bad. Very bad.