It depends on your needs.
The typical answer is to get the lens. But depending on the type of work that you are doing, and what you are missing the camera might be the better idea.
I just went from a 20D to a 40D. I have a few more lenses though.
For me, my 20D was nearly 4 years old, had been in the ocean twice and wasn't working quite well anymore. I wanted the LiveView (Macro Shooting), Anti-Dust (not a big deal, but I've found it useful at times), larger LCD (again for Macro), Faster FPS, I swear that I'm getting better color out of the 40D, but most people haven't seen a difference, I also needed a backup camera for trips.
I had been waiting for the 5D replacement, but after it didn't come out in the spring, I had to move on the 40D. When the 5D replacement comes out (or 6-12 months after it does), I will probably purchase one of them, and convert the 20D into an IR camera.
People have raised good points about the missing focal length, but with that type of glass, I'm sure that you have been coping for a while with the disparity, if you've been missing shots, then go for the lens.
In your situation, if it were me, and my 20D was in good condition, I'd probably opt for option 3 and either purchase the 135MM f/2 or the 200MM. (which if i stay within the constraints of the question, that'd equate to buying the 70-200).