Chapters 47 to 49 will be bundled with Volume 14 of the manga, which is scheduled to release September 16. What does this mean for the anime? Well, I have come up with a few different scenarios:
A. The second season of the anime will end at episode twelve. Since the Jun arc will end at episode eleven (the tenth episode just aired), the twelvth episode will be filler (most likely the one where he gets an email from a game company asking for his advice). It stops there, with no announced third season.
B. The second season goes PAST twelve episodes and decides to skip the Haqua and Yukie arc OR there is a third season announced. The anime can easily mention Yukie in a later episode. If the anime was extended to 24 episodes/a third season announced, we should see Tsukiyo + Minami + the entirety of the Tenri arc. If the Tenri arc doesn't take too long then there could be a novel character somewhere in between.
C. The anime goes past 12 episodes but does not follow the manga. Think about the original Fullmetal Alchemist series; it only followed the manga halfway through (Fullmetal Alchemist: Brotherhood changed all that though). After Keima captures Minami and Tsukiyo, an anime-original ending arc could be made where the ending is rushed by having Keima and Elsie trying to save Hell from something. In the ending episode all the loose souls would be captured and Elsie decides to stay with Keima in the human world (or something like that). This option is sure to displease A LOT of the fans of the manga (including myself).
D. The second season keeps on going well after 24 episodes and keeps following the manga. The best possible outcome, as we can be certain that it will cover the Goddess arc.
Going by what I know, I would put them in the following order, from most possible to least possible:
1. C - Manglobe's longest series is Samurai Champloo, which has 26 episodes. If the anime isn't very popular in Japan, an anime-original ending at 24-26 episodes would be a nice way to end the anime series without leaving fans (the anime-only viewers atleast) wanting more. It's the happy medium; saves the budget and the viewers are happy.
2. D - The anime would either end after the Goddess arc or keep on going as a weekly anime (like Naruto, Bleach, One Piece, Reborn, etc). The fans will be happy, but making an anime series longer than 24-27 episodes would require loads of money.
3. B - It is pretty weird that there is no season end date, especially considering that Deadman Wonderland, another one of their anime, is airing this season as well and has an end date. 24 episodes/a third season would reach the Tenri arc. The Tenri arc is an excellent place to START a season. If it ends in the Tenri arc, the preview should announce another season, like how season one did.
4. A - Considering the fact that ending at this point would be kind of anti-climactic without an announced third season, I don't see this happening. This is still a very big possibility though.
So there it is. Keep in mind that it may be possible that the anime does not end up being any of the four above. Regardless of whether the anime ends or keeps on going, us TWGOK fans will still love the series.