few things,
Moderns Game engines now use job/task based systems, they are no longer serial and inherently multithreaded. If you only see a few threads in PC games thats because of lowest common denominator PC specs.
Lots of game code very neatly fits into 4 wide FP vectors ( 128bit) but not 8 (256bit)
Xenons is already 6 incredibly weak threads
who said anything about Jaguar being "slow", Jaguar will offer IPC per thread around 6 times that of Xenons and those are "better quality" instructions ( RISC vs CISC)
Bobcat doesn't look that great these days because of 64bit FPU, this doubles latency(of the execution) for 128bit SSE2/3/4 and halves throughput compared to 128bit FPU ALUs that are in Jaguar.
And there will not be multiple cpu chips in the console. In fact, in durango there will be one chip, which is an APU. As for "Jaguar 8-core does not exist", Jaguar is integrated as clusters of 4 cores+L2. More than one such cluster can be integrated into a single chip by using a cache-coherent interconnect that attaches to the L2.
just to back this up.
During last years jaguar presentation for hotchips it was stated that the 4 cores and L2 are a compute unit, that the L1/L2 is completely inclusive(bobcat/bulldozer dont do this) and number of Compute units in a SOC was a SOC level decision.