The deadline for accepting the position or not (for the people initially offered a position) was a few weeks ago. I don't know for sure, but I would guess most positions have been reassigned, so if you have not heard anything by this point, it's probably a no. However, I have heard from past TAs that if you don't hear by June, you probably aren't going.
However, I would encourage you to reapply if you aren't offered a position. I applied three times for the Austrian USTA. Rejected outright the first time, alternate the next time, but never was offered anything, and accepted my third time. I would say, if you are an alternate this year, your chances are pretty high to be accepted next year!