I strongly suspect that the delay, if it eventuates, will be for marketing rather than purely technical reasons. AMD seem to be feeling very upbeat indeed about the 166MHz FSB Athlon XP family, and (in my estimation) are expecting them to last quite a while as the top dog on the desktop. On the other hand, they don't really have a serious entry in server space at all right now, so they have nothing to loose and everything to gain by getting the server chip out ASAP.
It occurs to me that they expect to be entering the server domain with their own, in-house chipset (or are they collaborating with someone like ServerWorks? I haven't been following this), which it's reasonable to suspect, given the excellence and stability of past AMD chipsets, will be pretty much a goer right out of the blocks. On the other hand, it would surprise me not at all to discover that AMD are dubious about the ability of VIA, Nvidia and SiS to deliver really solid, 100% stable new chipsets for the desktop market without a little longer to spend on development. So there might be a synergy there.
Thirdly, it seems that although there have been no tales of quality problems with the new process, volume is ramping up no faster than predicted. Some of their past process changes, notably the one from 0.35 to 0.25u that introduced the K6-266 and took them through the whole K6-II and K6-III family, went better than predicted and they started delivering ahead of schedule. It looks as though the current process change is not doing that. Given that (according to this theory) they are not getting a headstart on production due to a process bonus (like the one that kick-started the K6-II), I guess that's another reason not to hurry too much.
I notice that the Register has been running stories of "delays" and "shortages" of the new Athlons. This is complete bunkum: AMD themselves said way back in August that they were not expecting to ship retail quantities of the new XPs to the general market until November. (This was at an official training session Kristi and I attended.) The Reg simply has it wrong. If we get to mid November and don't see the new parts, then and only then will there be a "delay". Thus far, they have delivered exactly what they said they would deliver.