Disagreed. If anything, the GPU is the best candidate for early upgrading because product refresh improvements are both more frequent and (thus far, at least) more noticeable than any other component. That means finding the best performance/price value that fits your current requirements at any given time and then doing so again sooner rather than later with the savings is the way to go. I'd much rather buy a $220 GPU now and another one in a year and a half, than buy a $450 now and use it for 3 years.
All that said, the 560 Ti is absolutely worth it over the 560, but that's mostly because the 560 is a terribly pointless product and a not very good value.