Right. I was at a roller derby championship in Boston this week and the longest zoom I had was the 24-105 F4 Canon. I threw it on my A6500 to crop the extra reach. Indoors, flat lighting.I do event photography. I don't play around with F4 glass for this stuff. You can either wait for Tamron to announce something, something that they said they'd be speaking about Q1 of this year which hasn't materialized or get something now. Your choice. I financed mine. Get it used, save money and trade in some stuff you aren't using. I also really do not use iso performance as a reason not to get 2.8 zooms. If I can shoot at a lower iso range I do. F4 pretty much means I'm at 3200 at all times regardless of what I'm doing.
The autofocus was shockingly fast for an adapted lens, but I had the ISO up to 4000 pretty much the entire time. I couldn't really budge my shutter slower than 1/320, too, so it was a rough ride. Had I been on an A7S or A7iii, I could probably have squeezed up to 6400 ISO and not been devastated.
Do you think that Sigma 70-200 2.8 Sport is worth it, or are you getting what you pay for? Same price as the 70-200 F4 Sony.