DDR2 was out long before it got uptook well, at 400mhz and then 533mhz.
Good point. This entire discussion is exactly like what went on at the front end of DDR2. However, AMD was very strong at the time and did not immediately migrate to DDR2 so, DDR1 had a good bit of life left in it. DDR1 still sells fairly well.
Currently, Intel is MUCH stronger than AMD and Intel is moving to to DDR3. So, it's entirely possible that DDR3 adoption will take place more quickly than DDR2 due to the popularity of the platforms that use it.
Also, people in many cases make their arguments against a new technology based on some incorrect assumptions. They forget that not everyone upgrades for the same reasons. Your bleeding edge adventurous types are already all over DDR3. They are admittedly a minority but, they also do not use the same criteria when selecting the parts they will upgrade to.