Considering the worldwide sharp decline in the number of users of Sony cameras with the A mount during the past years, it is no longer profitable for Tamron to make lenses for the Sony A mount.

The future lies entirely with the Sony E mount cameras, which is why Tamron released the Tamron AF 28-75mm F/2.8 and a 17-28mm. 

In the future, even more lenses will be developed for the Sony E mount.