I hope it comes sooner than later. This would be so useful to a lot of photogs.
Here are the 24-70mm f/2.8 lenses with and without IS that are more than $1000.
$2,396.95 - Nikon AF-S NIKKOR 24-70mm f/2.8E ED VR Lens
$2,198.00 - Sony FE 24-70mm f/2.8 GM Lens
$2,098.00 - Sony Vario-Sonnar T* 24-70mm f/2.8 ZA SSM II Lens
$1,796.95 - Nikon AF-S NIKKOR 24-70mm f/2.8G ED Lens
$1,699.00 - Canon EF 24-70mm f/2.8L II USM Lens
$1,299.00 - Sigma 24-70mm f/2.8 DG OS HSM Art Lens for all mounts
$1,199.00 - Tamron SP 24-70mm f/2.8 Di VC USD G2 Lens for all mounts
$1,099.00 - Tamron SP 24-70mm f/2.8 Di USD Lens for all mounts
$1,096.95 - Pentax HD Pentax-D FA 24-70mm f/2.8ED SDM WR Lens
The Nikon with VR in late August 2015 was offered at $2399.95.
The Sony in March 2016 was offered at $2200
The Canon without IS in Febuary 2012 was offered at $2,299.00.
My guess is that the 24-70/2.8 with IS will be offered above $2,400 and be lowered to actual street price 6 months after release.
Next up a 16-35 f/2.8 with IS!