I respect your opinion with this, but I am going to use the Transformers as an example. When the animated Transformers TV series came out years ago the Transformer comic books were hot sellers in the LCS like the X-Men, then the animated Transformers got cancelled then like you say what will happen to the Walking Dead is Transformer sales dropped. Ok, you say that proves your point, but what happened to the Transformers was it never went away, and it rose again with billion dollar grossing movies. The same thing will happen with Walking Dead. Yes, TWD will eventually get cancelled, but someday they will bring it back as a trilogy on the big screen say like in 25 years?
People will then pay bigger bucks for TWD #1 in 25 years then they do now.
I can see young people who can`t afford TWD#1 now spending big bucks for it in 25 years.
So yeah your right it will cool down after the TV series is cancelled, but I see it rising again when they go to make TWD Hollywood movie blockbusters.
In the end TWD #1 is a winner.
Not saying that this wont happen but the situation you are positing requires many factors to align.
I would not say the bubble has bust but we have seen significant downward movement on issues number 1.