I'm absolutely sure there won't be a 70-200/2.8 STM as the 28-70 is not a 24-70 and the 16-28 is lightyears away of being a 15-35 or 16-35.
I can imagine a 80-150 or 70-150 or something like that.
I appreciate the trend of having an extra choice, the question is the compromise they offer VS L lenses.
For me it comes down to:
- IQ
- AF performance
- weight
- price
My big problem for many many years, is the unavailable IQ and AF performance without all the other unnecessary stuff. Most of the times I do not need weather sealing, iris ring, focus button, control ring, reduced focus breathing and all those bells and whistles. I'd say I don't even care about CA and corner sharpness as long as they are not terrible.
But since forever, if you want good IQ and AF perf, you have to pay and carry all that overhead.
...and in the APS-C world it has always been even worse, I had to use full-frame L lenses on D60-10D-20D-30D-40D - an attack on my wallet and my shoulders, yet half of the lenses were not used by the body when taking the photos. This has only changed due to switching to ff, not because Canon introduced proper APS-C lenses.