I just got this from a source:
Tamron wanted Techart to produce something similar to MC-11 and it would have been branded as a Tamron product. For some reasons that I don’t know, Tamron just gave up the partnership and the whole adapter idea. However, Techart is still going to introduce it to the market later this year, with their own brand. I’m not sure how much technical support they got from Tamron.
Just my two-cent: I think Tamron should focus their resources on making new native E-mount lenses. Their 28-75mm is a real hit and also well-known photographer Albert Dros seems to like it:
The good things really outweigh the bad things for me here. I’d say that this lens is perfect for landscape photographers who value light weight and sharpness the most.
Another new review by Dustin Abbott:
And here another one by Christopher Frost: