I'm going to say it as explicitly as I can: don't get too excited for the image above. The piece, by artist Gabz, came off of the UbiWorkshop Twitter, which wasn't actually a thing until yesterday. In fact, despite it now being active, we're still not 100% sure what it is. For a few hours, it covered a conversation that was going on between Cameron Stewart and Karl Kerschl, two comic industry professionals, but besides that we're still in the dark about the entire project. It's likely on purpose, considering the account's image is a question mark. What we do know, however, is that it linked to the image above, which is freaking awesome.
After some discussion on secret projects and NDAs with the two comic artists, the account updated with the image above, with only the promise that it isn't a part of Assassin's Creed: Brotherhood. In fact, before anyone starts waving the "Assassin's Creed III in Egypt" banner, it's worth noting that this is likely part of an as of yet announced Assassin's Creed comic book series, as Ubisoft has confirmed that it's not attached to any game currently in development.
So, in other words, here's a picture that's likely from a comic about a game. There, happy we got that over with. That's all we know right now, but we'll likely have more in the near future. Even if it isn't revealed at E3, expect some sort of unveiling in the coming weeks, if it'll even take that long. It's not like the comic industry is good at keeping secrets or anything.