Now that I'm fairly confident everyone got their t-shirt from the presale, the extra shirts are available for anyone who wants one. There are no Small or 4XL shirts, but at least two of all of the other sizes. Add a shirt to your cart then click checkout and it will tell you if your size is out of stock.
http://www.xs650.com/pages/store/
http://www.xs650.com/pages/store/