Well, I did not wait. I made a not-too-painful trade, a redundant wide-angle lens, as partial credit, and bought the Zeiss pre-owned 2/135 Sonnar ZF.2 lens. Initial impressions, just hand-held shots thus far, are very favorable. I even found that one of our energetic pups was not an impossible subject. (I have tremendous respect for photographers who shot active subjects before the advent of AF!)
This is my second long-time "grail" lens acquisition this year, the other being the Nikkor 14-24/2.8G. I am now in the interesting position of having achieved all of my major, long-term, realistic lens goals. I am not saying I have bought my last lens, but for the shooting I do now, and plan to try soon, I feel quite well-equipped, optically. My next significant purchase is likely to be something like a tripod head, or another Speedlight.
Canon 5Ds R/7D2/7D/5D/40D/1D2N; Nikon F6/D3s/D700/FM3A/Coolpix A. Lens selection undergoing changes; some favorites: Zeiss 2/135 APO Sonnar, Canon 100mm f/2.8L Macro IS and 135L, Nikkor 14-24/2.8G and 200/2 VR.