...they will develop either a 300 f/4 or a 400f/5.6 prime for m4/3 cameras. But scaled proportionately for m4/3. I would buy both in a heart beat. And no they wouldn't have to be huge and cost a bundle. Should be able to do both smaller than the equivalent Canon and for less than $2000. I am just so unimpressed with my 100-300 that I may get another 7D just for the longer end.