The amusement you get from the debate might depend on how dark your sense of humor is. I wouldn't be at all surprised if Biden suffers a stroke (staged or authentic) before or during the debates. No matter what he does you'll have a bunch of Democrats exclaiming how great his victory was in the debates. If it's too obvious his brain is falling apart, they'll come up with a medical excuse to withdraw him (something that only just now manifested, not a part of what we've been seeing over the past few months). Then they'll say even with that medical condition he was able to tear Trump apart in the debates, just imagine if he still had his health. The funniest thing I could see happening would be for them to replace him with Hillary through some emergency process.