OK. I just posted the prices of the Chips above and Whilst that of course is probably possible. You will/can spec a dual 12 Core With Enough Ram and a couple of decent Cards and it would cost you $20,000+
The benefits of dual CPU is overstated. The overhead and heat is really quite high. and pretty power inefficient. The speed is exponential the more cores the less over all speed per core.
I suspect the 12 Cores will be very expensive as it is and if they Did produce one and who's to say they won't in the future - I imagine building a dual motherboard into this would be technically challenging but may happen. It's entirely possible it could come out in 6 months... The original 12-core came out on it's own as I recall.
As for PCIe cards... what ones do you actually use? I am just interested to know what people actually need. The Red rocket card is one but that is not actually needed as this can shift 4K quite happily it seems.
More expansion boxes will come - perhaps even apple will come out with one. I've already run a 10m corning Thunderbolt cable to my garage. Storage and noise out there please