The sources of advancement in computer power have been more limited to raw speed at which the cpu runs vs. architecture advances.
Take the chart here for example:
http://www.netlib.org/performance/html/dhrystone.data.col0.htmlOn a DMIPS/Mhz basis, the early chips (towards the bottom), like 6502/8086/186/286 are more on par of 0.1DMIPS/Mhz. The newer chips, like Pentium, etc. are more 0.5 - 1 or 1.5 DMIPS/Mhz, over the course of 20-30 years. Or 5 - 15x.
In the mean time, the speed at which they run had gone from 4Mhz to 200Mhz, or 50 times, and even more if you benchmark against today's Xeon / Core chips.
So there is not a whole lot to be gained going from one architecture to another - I think our own numbers here show as well. The increase in performance comes more from running the chips faster and faster.
Plus, for many applications, faster isn't as needed as other measurements, like current consumption.