IBM has posted the first official information of the PowerPC 970FX (90nm PowerPC) in this PDF entitled "IBM PowerPC Quick Reference Guide".
According to the document (page 10), the PowerPC 970FX is the 90nm version of the PowerPC 970 (G5). A comparison chart reveals that the 970FX consumes 24.5W at 2.0GHz while the original 970 consumes 51W at 1.8GHz. The 970FX speeds are only listed as 1.4-2.0+ GHz, however, revealing no information as to the top speed of the chip, though the Bus of the new chip reaches 1.1GHz (vs 1.0GHz of the PowerPC 970).
The 90nm PowerPC is widely expected to power the next PowerMac revisions, and are currently being used in the recently updated Xserve G5s. The 970FX was first referenced in this rumor report but few other processor details accompanied that report.