Watch out captain! Cliff ahead! TheBrownCanadian was able to glitch out Assassin's Creed IV and make it look like a Spelljammer-style space pirate game. Anti-gravity engines were not that advanced in the 1700s after all.
Corporate Evil: here's a small but fun easter egg that ties together Assassin's Creed 4 with another Ubisoft game—Watch Dogs. You can see this yourself while hacking computers in the Abstergo offices in AC4. Video by MrSkillToKill2.
Many of gaming's biggest franchises have no endgame in mind—ask Nintendo when they'll stop making Mario games, for example, and you'll be laughed out of Kyoto. And the actual NFL is more likely to end before Madden ever does.