Posts by Lcrunyon and piggsy above have persuaded me to change my mind. All things considered, it's probably better that the new macro lens has a maximum aperture of f/2.8 or even f/2.0, even if those apertures are not used as often for macro work. First of all, I probably wrongly assumed that it was not possible or practical to do macro focus bracketing/stacking with a 100mm lens at f/2.8.... and while I'm sure it does start to be a
huge number of frames you're stacking (depending on how close and how big your subject is), I suppose people do it. But secondly, as piggsy said, I need to remember that in micro-4/3, diffraction affects image quality more and sooner as you stop down, compared to larger formats. So in order to try to allow more "diffraction free" aperture choices, in general it makes sense for all micro-4/3 lenses to have large maximum apertures. And there is a lot to be said for making a longer macro lens more flexible and useful as a general telephoto lens, and that means giving it a larger maximum aperture and adding the size/complexity/cost to make it perform equally well wide open and also stopped down. So,
not than anyone in the world cares what I think, but I will amend my earlier statement to, "I would prefer
f/4 f/2.8, but I won't be surprised or that disappointed if it is
f/2.8 f/2.0."
Dave