Obviously, sequential programs haven't been getting slower on new chips. However, the acceleration rate of single thread performance has been slowing, so even with all our tricks we're getting double in four years when it used to be every 18 months just by doubling the number of transistors on an IC.
AMD recently sacrificed some single-threaded performance in order to achieve an increased core count. Whether or not that was a good move or representative of the industry as a whole is open to debate, but it does occasionally happen.
