Will S2 be available for Christmas?

It depends where you plan on purchasing it. But yes, being it's a new product release and with the Holidays approaching, it likely will be limited. And overall how Apple keeps up with production is a factor as well.

 

Right now, my location has a dec 1st pickup in stores. Online is still 3-6 weeks depending on what model and size your looking for

 

Check istocknow.com Much to my surprise, they have a ton in most Apple stores around the country now.

 

Last time around, the sales in November came about four months after the stores and retail partners had stable inventory. This time around, stores and partners will probably not receive stable inventory of most SKUs until late November. So, they may not discount, since supply may still be scarce.