A recent FCC filing for what seems to be an updated model of Samsung's Nexus S has given some credibility to the possible existence of Android 2.4.
Engadget recently noticed the listing for the Samsung GT-i9023, the outline of which appears to perfectly match the current Nexus S. Coincidentally, the Nexus S also happens to have a very similar model number - GT-i9020. In addition, Engadget notes that the GT-i9023 also recently passed Bluetooth SIG and Wi-Fi Alliance certification, so this is definitely a real device.
What makes this story interesting, though, is that it gives weight to a video recently recorded by German tech site BestBoyZ which seems to show a Nexus S running Android 2.4. The baseband version displayed on that phone begins "i9023," which would seem to refer to the new Nexus S model. This is still well within the realms of speculation, but if the GT-i9023 is indeed refreshed Nexus S hardware, then it suddenly becomes pretty reasonable to think it might be running a refreshed version of Android too.
The Nexus S isn't the first device to be caught apparently running Android 2.4. At last week's CES, Sony Ericsson's upcoming Xperia Arc was snapped with "Android version: 2.4" on its "About" screen, though this was later dismissed as a "misconfiguration" by the manufacturer.