"I think Windows 7 is a fine operating system and I have been very satisfied with it. In truth, I have been so satisfied, I cannot think of a single feature that Windows 8 could possibly have that would compel me to, once again, upgrade my operating system."

Let's try,

"I think Windows XP is a fine operating system and I have been very satisfied with it. In truth, I have been so satisfied, I cannot think of a single feature that Windows 7 has that would compel me to, once again, upgrade my operating system."

Not my opinion, but the substitutions nicely sum up the feelings of the XP die-hards. If you can feel that way about 7, can you see how they feel that way about XP? As you say, sooner or later MS will leave XP behind; they'll do the same thing with 7 eventually. Will you still feel there's no reason to move on when MS abandons it too? When hardware manufacturers no longer write drivers for it, especially 32-bit drivers in an increasing 64-bit world?

I haven't seen 8 yet but regardless, MS and vendor policies will continue to drive OS migrations for the foreseeable future.