http://www.dailytech.com/AMDs+45nm+O...rticle5984.htmShanghai is apparently more than just a cache-bump. AMD's documentation explicitly claims Shanghai will be the company's first 45nm processor. However, with a die shrink additional cache is one of the immediate architecture options as the smaller node allows for more transistors to fit on the chip die. Shanghai features 6MB of L3 cache.
Shanghai will also use the Socket 1207 interface, suggesting existing motherboards will have the opportunity to upgrade to Shanghai processors -- AMD processors are typically designed to work with existing motherboards on same-socket interfaces with simple BIOS updates.