A source close to the subject has told Pocket Gamer that the games have been removed permanently so that Disney and Lucasfilm can focus on other, higher priority titles (like the recently launched Clash of Clans-alike Star Wars Commander).
Ian Marsh, of Tiny Death Star developer Nimblebit, told Pocket Gamer that he was not told about the game's removal before hand. He said "my assumption is they don't feel it is worth it to maintain the game any longer."
He also added that the game was "a significant source of revenue for us, so it stings that much more."
We called Tiny Death Star a "clever blending of two licences" in our Silver Award review. The "forgettable" Assault Team got a six.
Both games will still work and can be accessed from your Purchased tab if you're on iOS, but they won't be updated and new players can't get them at all.(Thanks to Gamezebo for first spotting the games's removal)