Due to the prep time involved in creating the artwork, having them screen printed, etc, I don't foresee any new clothing products for this season. But... all this talk certainly has me excited about offering something new in the long-sleeve and/or hoodie department for next year!
(and if that doesn't happen, I'm sure someone will dig up this thread next year and quote me on it)
Personally, I wear tshirts year round. In the cold fall and winter, I layer them up with a long sleeve thermal shirt underneath. It works well, because... ya know... a ZP tshirt looks great at Christmas time, with red or green sleeves.