It certainly makes for some fun speculation doesn't it?
Can it compete? There's some good possibility. There's a large number of factors that end up playing a huge balancing act game for different topics such as reliability, manufacturability, performance, and price. I don't recall the 8641 having integrated USB, so you'll need at least a PCI-Express/USB bridge to add that and be more completely comparable with DiscoveryV+G4.
the G4+DiscoveryV combination, as well as G4+tsi108 combo, will have lower BGA pin densities than 8641. This means the 8641 will require smaller and closer togather PCB traces to fan out the chip to the PCB routing so it can connect to other chips. There's PCB manufacturability and yield issues that te 8641 will be harder to build, and thus somewhat lower PCB yield, and thus mroe expensive. The 8641's higher BGA density may also require more PCB layers for the BGA fanout, which again would increase cost and affect manufacturing yields since more layers means more vias, which means more opportunities for a via to go bad somewhere. And which is more engineering effort, a single chip with more and higher-density pins, or two seperate chips with lower pin density and possibly fewer PCB layers?
Though the 8641's internal MPX bus runs much faster than the external bus to either DiscoveryV or tsi108. This would theoretically offer higher performance, which would be desirable and perhaps be worth some amount of possible higher price for the single chip and more expensive PCB, compared to the G4+northbridge combo and the associated PCB price.
And then, setting aside the PCB, how will 8641 price compare to G4+DiscoveryV or G4+tsi108 combo price? Or swap the G4 for a G3 in the combos.
Some of these things aren't known yet, some can be guestimated about. If you want the smallest possible system design, 8641 is the way to go. If you want the least expensive, we don't know yet which would win.
