Nexus S, which happens to have a suspiciously similar model number of GT-i9020.
Here's where it gets interesting, though: German site BestBoyZ just reported a video of a Nexus S in the wild a few days ago that claimed to be running the rumored Android 2.4 release, and the baseband version in the About screen included the text "i9023." This new model number also just very recently received both Wi-Fi Alliance and Bluetooth SIG certification, though there's nothing particularly interesting in those filings. Oh, and one other random tidbit: a number of European retailers are listing the i9023 already as a "Black Silver" Nexus S, so it's possible that this will simply be a new color scheme -- but would that really necessitate a new FCC filing and model number? It's also conceivable that Samsung is taking the occasion of 2.4's release as an opportunity to tweak the Nexus S a bit -- maybe add HSPA+ for T-Mobile, something to that effect -- but at this point, it's pure speculation on our part. Feel free to drop your conspiracy theories in comments, and while you're at it, check out BestBoyZ's video after the break.
Note: The Vibrant 4G is a good thought, but this device seems too rounded -- it matches up perfectly with the Nexus S.