If the Metro APIs include anything capable of running binary code, Chrome will probably be developed for it. Given Microsoft's recent history of being careful to display monopolistic behavior, I'm sure they'd allow Google to distribute Chrome through the Windows app marketplace.
That depends entirely on the good graces of Microsoft.
On a less snarky note, the WinRT based tablets (the ones coming out in a week or so) can only run metro apps. Unless Chrome puts a version of the browser in Microsoft's marketplace, it won't be available for use.