http://sigma-rumors.com/2014/09/sigm...ional-details/

The new Sigma 150-600mm f/5-6.3 DG OS HSM belongs to the Sports category of the Global Vision line.

Seeing a new telephoto zoom lens is not surprising, but we were not expecting an exact match to Tamron’s lens in terms of range and aperture. Although the Sigma lens is not any faster, the company chose to go higher end on a few aspects, targeting professionals. This is why the lens is included in the Sports category, and not Contemporary.
More information is coming on the new 1.4× and 2× teleconverters as well.

Highlights
  • The lens is larger and heavier than the Tamron 150-600mm f/5-6.3 due to bigger glass elements.
  • It features weather sealing.
  • AF and OS have been optimized (see below).