I think you've made a good decision - but then I would because it's what I did in the same situation.
If you look at the performance of one particular lens - say the 80-200mm f/2.8 - through its various incarnations you'll see that the latest AF-S version hasn't changed much in terms of optical quality over previous versions, so it would seem a speculative future lens that made significant performance improvements over current versions would be massively expensive. I think your investment in high quality lenses should be a safe one.
The areas where you might be cutting yourself off from future developments are more associated with usability: the inclusion of technologies such as AF-S and VR which now seem to be appearing in more of the range, and the possibility of more compact long focal length lenses that use diffractive optical elements. (Yes, that's a link to you-know-who. )