Probably not a popular idea on a Castle site, but I'd really like to see more Galaxy Squad. I think GS is the best non-licensed sci-fi theme since Star Wars came out, and I think GS is the best theme of 2013. The set designs are simply wonderful, and the theme is packed with so many great ideas: bug figures, giant bugs, robot figures, giant robots, vehicles with detachable sections, the bug larvas, cocoons, and the four colored squads. There is a lot of potential for building MOCs based on sci-fi properties like Pacific Rim, Starship Troopers, and StarCraft.
I was honestly surprised to see a second wave of Galaxy Squad sets, especially so soon. I have no idea what plans, if any, TLC has for the future of this theme, but here are some ideas for expanding it:
Wave Three: Rather obvious, but a third wave in 2014 would be great. Maybe four more sets, one for each squad. Furthermore, a new wave should introduce a second human figure for the red and green teams because they each only have one at the moment. Preferably at least one of those new figures would be female to prevent Galaxy Squad from looking like Smurf Village. One of the four sets should be a large hive structure for bugs; obviously this would be the one containing the red squad figures.
Polybags: The orange and green squads each have a polybag set available. Seems only fair to do one for red and blue eventually.
Battle Pack: A small set featuring four generic soldiers, one from each colored squad. Possibly another pack for bugs.
LEGO Exclusive: Many themes are given a large exclusive as their swan song. See Medieval Market Village, Kingdoms Joust, Haunted House, Diagon Alley, Imperial Flagship, etc. What is needed here is a human base for all four squads. Perhaps four small modular bases, one for each squad, that may be connected together in a variety of configurations or used separately. Bonus points if each section has instructions for an alternate module. Possible module ideas: Sick bay, communications, repair/hangar, mess hall, defensive turrets, bug holding facility, armory, and robot recharging stations. It would also be nice to see some new figures in a set like this. Possibly new named squad members, generic soldiers, or non-squad staff members like medics and a space chef. Finally, a giant centipede-like bug crawling on top of the base would just look awesome.
Maybe that last one is something for me to do on my own.