Sony Alpha Rumors still says it's coming.
My gut is that a 16-28mm f2 would pair very nicely with the 28-70mm f2, and then if you need something wider, you can add in the 12-24mm f4. Maybe we will even eventually see Sony make a wide angle zoom that goes down to 10mm f4. But, if you need 12mm f2.8, then IDK if it makes as much sense to pair the 12-24mm f2.8 and a 16-28mm f2 together.
In theory, a 16-28mm f2 could replace a 16-35mm f2.8, 14mm f1.8, 20mm f1.8, 24mm f1.4, and 28mm f1.4 in someones bag.