Leaker HowToFly just tweeted this:
Tamron is going to announce a NEW lens next week,a fast wide angle zoom, nice companion to the current 35-150mm F/2-2.8 Di III VXD.
Asobinet speculates this might be a 17-35mm F/2-2.8Di III VXD. I got no info about such a lens but surely it would make sense!