According to reports, Tamron will introduce a new 24-70mm f/2.8 Di VC USD G2 later this year. The new version will be a replacement for the current 24-70mm f/2.8 Di VC which was announced back in 2012.
As pointed out by Photo Rumors, this is a logical next step as Tamron updated the 70-200 f/2.8 VC to a new version early in 2017.
Sigma recently announced a 24-70mm f/2.8 OS Art series lens that we still can't order, so Tamron likely has to follow suit.
Some folks are still clamouring for Canon to release a new 24-70 f/2.8L with IS.