i looked through AMD's site and i havent found anything pointing either way... but it would only make sense to give FX the 90nm architecture. being as it is marketed as overclockable and all, and it wouldnt look good of a 3500+(winchester) could overclock better than an FX costing twice as much, so using logic id say they are going 90nm on new FX's.
CORRECTION:
AMD will release FX on 90nm in first half of 2005 according to their roadmap. and with dual core in second half of 2005
CORRECTION:
AMD will release FX on 90nm in first half of 2005 according to their roadmap. and with dual core in second half of 2005