That would be a highly theoretical number and based on shader power exclusively, i.e. TMUs are quadrupled, and we (well, at least some of us) don't know exactly how much the architecture scales with the multi-cores.
Strange, as IMG have repeatedly stated publicly that their MP I/P scales virtually linearly (i.e. >95%), 2 cores gets you almost twice the peformance, 4 cores gets you almost x4. They state on their website that a 543MP4 @200Mhz give 133M polys per sec, which is slightly less than x4 the spec for an SGX540 (which as I recall is 35M).