There was nothing wrong with those systems when we decided to upgrade.
This last upgrade we switched to top of the line/best in class hardware and hope to resist the urge a little longer prior to upgrading.
I really notice very little performance upgrade this past 3 year cycle. What's really new?
So, until I can buy a nCore processor supported by applications and operating systems that will utilize them - I don't see the need for mid-grade consumers to upgrade.