I'm not so convinced. Knowing what specs the simulations give you is one thing. Knowing how production silicon will behave and what you'll have to do to mitigate yield issues and thermal surprises is another thing altogether.
I believe they have a target in mind and a concrete design on the table. The question is whether they'll hit their target, or what they'll do if it doesn't go as smoothly as expected. Would they turn clock speeds down? Ship something that runs hot and is potentially failure prone? Or slide their schedule? These are questions every project involving significant custom silicon faces this far out.
... and I don't buy the half-precision argument at all. That's just madness. Can you imagine the backlash if people held off purchases for a year to wait for a less powerful machine? Microsoft may misjudge the market from time to time, but they know full well that would be the end of the Xbox brand.
