I have it on semi-good authority (someone who has been both right and wrong in the past) that it's a APS-C zoom, and on dubious authority (someone who was right a couple of times but mostly been wrong) that it's a mirrorless-specific zoom.
If I were to put money on it, I'd bet on APS-C general-purpose zoom. That's something they have a few of in the old style of lens, but not in the modern line. It's also something Sigma has had fair success with, as well as Fuji. Going on what I've been told (again, somewhat sketchy sources) and what their line-up currently looks like and feels like it's missing, that's what feels right for Tamron.
Then again, nobody would have guessed they'd go with 45mm or that Sigma would make a lens like the 24-35 f/2, so, hey. These two companies are capable of pulling something completely random out of nowhere.
Sporgon said:
but given that Tamron have introduced the 85/1.8 I'd imagine that they wouldn't begin their new prime series by having two such similar focal lengths - unfortunately.
Reminder that Canon did exactly this, with the 100mm as the spearhead of the then-cutting-edge EF lens trio, and the 85mm version coming along just under a year later. Then they also piled on a macro version, too, which would also fit Tamron's line. (85 VC, 90 VC macro, so add a 100 VC and they're duplicated Canon.)
All that said, that was the early 90s and these days 100mm isn't anywhere near as popular as it was then. While there's a small market for it, it probably wouldn't be worth Tamron investing R&D into a 100mm prime now unless they were able to very quickly and lazily re-use parts from the 85. (The same way Canon made the 85 out of the 100.)
I'd love a Tamron 100mm f/2 VC 'cause god knows the existing Canon one could do with stabilisation, weather sealing, and a little more consistent rendering across the frame, but I doubt we'll see that from Tamron until they have filled every other niche first. I expect we'd see a Tamron 28mm before we see a Tamron 100mm.
