I don't know why AMD doesn't use quad-pumping, however 800mhz DDR will theoretically provide identical bandwidth to QDR 800. In the real world, DDR will probably come out on top because of it having double the external clock. Since this thread is about speculating AMD's future, and very few seem to actually have done so thus far, here's a run down:
Q3 2003: AMD's Athlon 64 will be released. AMD users will rejoice, but their happiness will be short lived. Expect these chips to have very low clock speeds (1.6ghz-2.0 MAX,) but very high, and falsely so PR ratings. They may come out with some mysterious 3 digit rating also. Also expect very overclockable Bartons, which will probably not be able to hold their own too well because...
Q4 2003: Intel will release the Prescott. This processor will deal a heavy blow to AMD. It will be fabricated under a .09 micron process, so expect very low voltage draw, very low temps, and thus incredible overclocking potential. Not to mention 1 MB of cache, and just maybe a 1066mhz quad-pumped front side bus.
From hereon, Intel will clearly hold the upper hand until:
Q2 2004: AMD will release the San Diego. .09 micron and 1 mb cache. Expect 1000mhz or higher DDR fsb. DDR II support is iffy. AMD and Intel will be very equal at this point in overclockability and performance. Sure, flame wars will continue, but they'll just be splitting hairs. However, the 64 bit bus will provide much potential for AMD, breaking the 4GB memory barrier that Intel will have to live with. The 64-bit PCI bus will allow for far greater performance in graphics processing, among other things.
This is about all I know. In Q4 2004, Intel will release the Tejas, supposedly with 2MB cache and built around a 775 pin socket package. AMD will continue using the San Diego core.
In the short term, I'd advise all AMD fans to buy now. The Prescott will overshadow both the Bartons and Clawhammer. The Clawhammer will very likely be outperformed by the Barton itself in 32-bit apps, and as we know how well the Thoroughbred does against a Barton, the Thoroughbred may surpass all Clawhammers. The Prescott's .09 um archictecture will be all it will need to completely surpass AMD from an overclockers point of view. The Prescott, however, will most likely be outdone a few months later by the San Diego. Which side of the fence you want to jump is up to, but you'd probably be happy with both. I haven't seen one person ever whose been disappointed over a choice between AMD and Intel; but I've seen the formation of numerous fanboys. Basically, it's all good; no matter what you choose, you'll be happy.