Ok so Tartarus Arc is coming to an end on chapter 416, and it looks like we're nearing the end of the series. The only things that are left are Zeref (and his relation to Natsu), Acnologia (and his past), E.N.D, Lumen Histoire, Layla's Death, and the Wizard Saints and Ishgal Gods. I think the next arc should involve the world left behind with "The Legacy of Tartarus".
Note* This is All Opinion and is not CANON.
Civil War Arc
the world is probably changed is several ways. The Magic Council is destroyed, the world nearly lost all it's magic, most of the current and former Magic Council Members died, along with several hundred people during Tartarus' battles.
After the near loss of Magic Power, the world would probably be in a state of fear, paranoia and chaos.
Even during rebuilt, there is a split in the number of Wizards Saints to form their own organization to take control of the magical world. They believed that the Magic Council was corrupt and incompetent so they decide to change it. Not only the Wizard Saints, but a large number of Guilds, Corporations, Nations, Political/Criminal/Independent Groups, and Individuals.
Loyalist Saints: 3
Separatist Saints: 7
- 4 other Wizard Saints
- 3 other Ishgal Gods
For Fairy Tail, they are currently in a state of recovery from their battle with Tartarus, Natsu, Gray, Lucy and Wendy was still depressed over Igneel's, Grandeeney's, Aquarius' and Silver's departure. They now have to get over their loss and face this new threat.
Also Jellal and the CS + OS are fighting prevent this Civil Crisis, how ever they are in trouble with their fight and is brought to Erza's attention that she might lose Jellal forever.
Plus Maybe information on Layla Heartfilia.
I once had a blog depicting my thoughts on each arc and with Tartarus Arc being about Pain, I think this Arc should be about "Healing". As in Are heroes get over their depressed states and move forward.