You know the answer to that really. DR3 if released mid cycle in a consoles life would barely raise an eyebrow. It will sell well as king kong did when the 360 came out, not because it will be stunning but there's little else on offer.
As much as I like to buy new things is there really not enough due this quarter on the 360 to make this a must have play? Surely it makes more sense to let others iron the bugs out and see where these consoles sit against each other.
There will then be a ton of second hand DR3 in the trade in bin if you really feel the need
When the 360 came out I was ready for a new system and didn't have much in the way of games to play. This time there's plenty, games like AC4 I can't see the game has been built that well for a new console so you may as well play it cheaper on the 360 and wait for a proper optimised version next year, same with COD.
So in short, no
ps I go through the same dilemma daily, luckily I'm tight and my brain rules my wallet.