I, too, am frustrated with the lack of long lenses for the 4/3 system, and am thinking of switching because of it. In my case, I would probably go to Canon, with their 500mm and 600mm lenses.
When I chose Olympus back in 2006, they weren't making any long lenses then either. But I thought that would change. I figured the 90-250 and 300mm lenses would drop into a reasonable price range (there's no reason even a great 300mm lens should cost over $6000, especially in the 4/3 system where the front element doesn't have to be as big to get to f/2.8); I also figured someone, maybe not Olympus but at least Sigma or Tokina, would come out with something like a 100-400mm f/4. But instead, the only long lens for the 4/3 system -- the "Bigma", Sigma 50-500mm -- went out of production, and nobody has stepped in to fill that space. There's just nothing for sports and wildlife photographers, at any price.
This really ought to be the 4/3 "killer app." Something like a 500mm f/4 or a 100-400 f/4 \ would give us the same reach for bird and wildlife photography that Canon and Nikon have, in a much smaller and lighter package. But instead, we can't get into that focal length range for any price at all, there simply are no lenses out there. It's baffling to me. And frustrating. On a recent trip to Yellowstone, documented at
http://www.creekcats.com/pnprice/YellowstoneInWinter/Photos.html I was reasonably satisfied with my Olympus...but not so satisfied that I didn't envy the guys with, say, a Canon 7D on a 500mm f/4 lens. For example, my shots of river otters are OK...but some of theirs are spectacular. In fact, for the otters I am able to compare my photos with the ones from a Canon photographer who was standing right next to me, shooting exactly the same scene at exactly the same time. He's got the "35mm equivalent" (I hate that ridiculous terminology) of an 800mm lens, with 16 megapixels giving plenty of room for cropping. Even with a 1.4 TC on my 50-200mm, I've got less reach and fewer pixels. Yes, it does matter. Quite a bit, actually.
I think the 4/3 format has a lot of advantages, mostly in terms of portability, which is in fact an important criterion for me. If there were only a long lens available, I'd probably stick with the system. But instead, I think that before my next big birds-and-nature expedition I will probably sell all of my Olympus gear and buy Canon instead. It's really a pity.
So: yeah, I understand your reasoning, and I, too, am likely to switch systems, all for lack of a long lens.
