The console's "Xenon" 65nm CPU however, according to Chartered Semi, will be available by mid-2007 and so in theory a version of the console with a 65nm CPU and 90nm GPU could be available in the next few months.
Microsoft will want to begin using the new, smaller chips as soon as possible because the chips run cooler and that will help in redesigning the console's interior for lower costs and higher reliability.
The changes of instituting the new chips will eventually make the 360 cheaper to manufacture and those savings will be passed along to the consumer eventually when the console drops in price.
Basically, wait until the 65nm CPU and GPU are both in the console, as they new units will run cooler, and last longer.
Source:
Arstechnica