I love Walking Dead. I was an early adopter. My collection ran back to issue #1 of buying it off the stands. I've bought and read every issue since. All that being said, take a breath.
#4 should scare the living mess out of you if you are concerned with long term growth. Spikes beget spikes in the inverse.
As for "generations to come"....do you know a lot of people that want "Whiz Comics" right now? That comic was one of the original juggernauts, selling nearly 1.4 million copies PER ISSUE at its peak...and was GONE within a decade of those sales figures.
That was our parents and grandparents generation. Do you see anyone outside of a few GA collectors who gave a hairy rat's about Whiz? If they did, and if current success was a guarantee of future quality, sales and popularity, Captain Marvel would be the biggest book going today. Books come, they go, no matter how popular or hot or great, tastes change, trends change, nothing lasts forever. Marketing, support, and fresh stories are integral to success. There's no guarantee WD will have any of those three for any guaranteed period of time.
Have a little perspective.
The voice of reason...
This is the message board.
Ain't nobody got time for that!