As soon as NVIDIA GeForce GTX 570 was officially introduced, water-cooling component manufacturer started to think about production of a new full-cover waterblock. However, if you take a closer look at GTX 570 you can see it has absolutely same PCB as GTX 580 with all design improvements inherited. Even the lengths of the cards are identical.
The only PCB differences is the absence of two memory chips in GTX 570 design as well as some power circuitry was cut. But that does not effect the possibility to use GTX 580 waterblock on a GTX 570 card. It is, however, true for reference design cards only!
German manufacturer, Aquacomputer, has confirmed this fact by showing the results of Aquacomputer Aquagrafx GTX 580 full-cover waterblock performance on GeForce GTX 570 graphic card. The block fits the card perfectly.
P.S. Shortly after, the same fact was confirmed by other waterblock manufacturers.