Okay, so several RvB fans have noticed the number 57 popping up throughout the Chorus Trilogy and think it's leading to something that might happen this season. I think so too. Here are a few links regarding this topic (the Tumblr link is particularly interesting):
Based on what I've read, many think it's about the return of Junior or the aliens in general. Episode 57 is the first episode where the Alien is seen and S5E7 is the first time Tucker meets Junior. With the Chairman explaining that humans are still at war with the aliens in S13E1 and the alien ship the Blues found in Crash Site Crashers, I think Junior/aliens may somwhow make a re-appearance.
However, the main problem with this is that Elites are not playable characters in Halo 4, so if Junior is coming back he'll most likely be seen in CGI. I personally don't know if RT is willing to use CGI for one character for that long. I'm not saying it's impossible, it will just take a lot of time and money. BUT, there's a large animation team for RvB13 this year so maybe they can do it.
Anyway, what do you think 57 will mean?