Delaying it to get one over on the competition sounds like BS Console Wars stuff rather than reality. Microsoft and Sony don't think that way, they're not plotting schemes against each other like this.
Whatever schedule MS has in place for releasing and distributing dev kits has surely been in place for a long time. Whether they're meeting that schedule or not only MS know.
They certainly try to be ahead of the competition and claim best machine. But through ways of either being more willing to subside the HW or being more efficient on the contracts and volume so they save some more on the cost and can have that turned either in like a 10-20% power advantage, 50 USD less price for same subside or use that saved money to grant more exclusives, invest in their studios, etc.
What they don't do is delay their launch 6 months giving the company that beat them 3 times time to get traction just to be a little stronger. Sure they could delay 2 years and have a significant more powerful HW, but would still probably be same tech so all that difference won't be that noticeable but missing on the market for 2 years will (while X1 is dwindling).
duduspace11 "Well, since we are estimating costs, Pokemon Red/Blue did cost Nintendo about $50m to make back in 1996"
Mr Puggsly: "Hehe, I said good profit. You said big profit. Frankly, not losing money is what I meant by good. Don't get hung up on semantics"