We've been seeing "Galaxy S3 leaks" for a while now, but it turned out all of them were fake. A new leak that shows a much better looking Galaxy S3 design may finally reveal the real phone, although there's still a small chance it could be fake of course. Nothing is set in stone before Samsung actually announces it themselves.
The reason why I think it could be real is because it looks very good design wise, and also because it looks more metallic. Samsung has hinted before that they may go with a metallic body for their next-gen Galaxy S. By far the biggest complaint about Galaxy S devices has been that they're too "plasticky", which has more to say about how it feels in hand than the material it uses.
For example the HTC One X is also made out of a plastic material called polycarbonate, but it feels a lot better and more solid in hand than Samsung and other manufacturer's plastic cases. But so far the best feeling and the most solid material has been the aluminum cases that HTC uses in most of their devices, and Samsung may have finally started using some similar metal (or the same for all we know so far), which should give their devices a much higher premium feel.
The leak also shows a May 22nd date for an announcement, which means Samsung might actually launch the device sometime by the end of June. That's almost 3 months from now, and that does feel strange that we'd see a leak so early for this device, especially one with such a fixed date so early on. But maybe the explanation for that is that Samsung themselves made this easy to leak, because they don't want too many people buying the HTC One X.
So this leak seems awfully convenient, because it shows the fans exactly when the Galaxy S3 will be announced so they know how much longer they have to wait for it. I can't say I blame Samsung for this, but the wait better be worth it, and hopefully they will unveil a device that is significantly better than the HTC One X, if people have to wait that much longer.