I think the upgrade path is more about consumer electronics than photography. It feels a great deal like the cycles in computing.
And that's because they ARE computers, and just like the shorter and shorter research-to-production cycles in PCs/tablets/phones, cameras now have exactly the same cycles.
Takkun...the pace is part of the problem. As I remember those early days the major camera companies made introduction of new equipment no more than annually. That being said there was a far amount of "churn" but at a slower pace.
Computers/Software upgrades ramped slowly at first and then picked up momentum. I personally think a great deal of digital photography marketing comes from the personal computer/apple play books.
And the pace, in the "old days" was much slower as there were actual parts to be spec'd and machined on assembly lines. Now it's merely re-arranging printed circuits. For that reason in the "old days" much of the technology progress was modular... and didn't require replacement of the camera body. The Nikon F with the removable finders comes immediately to mind; there were at least three iterations of finder for the original F body, and a couple for the F2 body which was released, IIRC some ten years after the F. Leica released similar "upgrades;" the various iterations of the Meter MR and Visoflex for example, which left the core technology intact.
And in early digital, each upgrade cycle brought tangible gains in speed, image size, color rendition, and resolution. Now 15 years into the product cycles, we're seeing relatively small, incremental changes in technology rather than revolutionary changes. The technology is maturing and it's increasingly difficult to replicate the early large leaps as research labs and manufacturers are bumping into the current limits of physics.
I am not an early adopter any more, having learned from the school of hard knocks in the early PC realm. While I have done iterative upgrades in my photo equipment, those upgrades were driven by market trends from client demands rather than equipment manufacturers. The technology is now at a point where, barring some unforseen techno-breakthrough that rewrites the current understanding of physics, my '08 M8 and my '11 M9-P will remain competent image-producers well into the next decade.
I'm not a luddite, but neither do I have a need to have the latest and greatest. I buy lightly used technology so I don't have to pay the depreciation. I'm definitely NOT on the 'bleeding edge." I only recently upgraded my iphone from the 3gs to a 4s shortly after ios7 came out. I do have an ipad, but it's an ipad 2. I build my own PCs with the level of components I need to do the job I need the machine to do. I have a 32" LCD TV, but it's about 8 years old, and I bought it after the prices dropped from $4k to $900. I look at cameras the same way. I'm definitely NOT in the camera manufacturers' target advertising audience.