Weeeeellllll the main issue is having enough readers to sell stuff to. We have a good chunk of folks coming by the site every day now but I'm not sure it's enough to support the minimum orders for stuff like T-Shirts and the like.
There's also the issue of coding it. We intentionally left it low on the list because we knew that it would be awhile before folks were clamoring for our wares.
I've been thinking about prints though... so we might do some of that soon.
If you want an "Rx" T-Shirt we have a few left over from NYCC. Send me a PM with your size and address and if we still have one in your size we'll get it out to you as a thanks for all your hard work.

In short though, the answer is soonish which isn't much of an answer I know.