We have the rather awesome Olympus 40-150mm 2.8, with a price tag to match that awesomeness, we have a 300mm f4 on the way, which will no doubt occupy a price range at least that of the 40-150, and a Panasonic 100-400, which is again shooting for extreme focal lengths but with little regards to light gathering (but rumored to still have a hefty cost attached). I might be alone here, but is a 50-200mm f4 not a good idea? It wouldn't be too huge or heavy, and it could occupy the significant middle ground between the generally cheap/slow consumer variable aperture zooms, and the 'pro' offerings with pro price tags. The Panasonic 100-300mm f4-5.6 is the obvious elephant in the room, but whilst it's a solid lens it's doesn't have a fixed aperture and has a rather limiting 100mm starting point. I used a Sigma 100-300mm f4 extensively in my DSLR days and it was a brilliant compromise to fill exactly the gap discussed above, and obviously Canon have a very popular 70-200mm f4 which on an APS-C body occupies a similar focal length. I had thought about a prime, occupying the large space between 75mm and 300mm that we currently have, but a zoom would no doubt be more marketable and therefore have more chance of being priced reasonably.