Maybe can hope from Tokina or Tamron? Tokina seems to be leaving "wide angle only" kind of approach so who knows...I would devestated if it was tamron as I think their quality is horrible, sigma seem to be a large margin in front in this department, I guess we will see if tamron have stepped up their game with the new 24-70 IS they have coming out.
Judging by the exterior of Tamron's new 24-70mm f/2.8 IS lens, it certainly appears
that they've put more effort into it. It will be interesting to see how it stacks up. Not that I think it'll be close to Canon's 24-70mm f/2.8L II, but if it's better than the Mark I, with IS, it could
be option, depending on the price.