It's also possible that there are First Civilization humans still alive somewhere and AC4 is the quest to find them. Obviously the First Civ humans rebelled and were able to defeat the "Gods" or survive over them while they all panicked over the Solar event.
I would hope that AC4 puts a little more emphasis and strength on the importance of the "present" events. Obviously, it's hard to top "The Truth" but it made for one of the most intriguing twists in game storyline history. I would like to see Ubisoft go back and repeat that. The Present time sequences always did a good job of drawing a little intrigue, but I found myself bored with them during AC3. I did like Juno's little history lessons but she was the only interesting character of the whole bunch.
Kotaku posted an article from one of their editors who has spoken to Ubisoft about AC4. He makes a few comments that should help people know that Ubisoft is taking the feedback from AC3 seriously:
https://kotaku.com/5988249/be-excited-about-assassins-creed-iv-and-be-skeptical
A few key take-aways:
-Kenway is charismatic and bold. Like an Ezio v2 but not quite. Should make for better player attachment to the character.
-AC4 was roughly begun in development in 2011, somewhat alongside AC3.
-The three main cities: Havana, Nassau and Kingston will have unique "looks" and not look bland and alike much like Boston and New York did.
-Approach to some assassinations will be more open-ended, much like the original AC.
-They are pushing "no loads". The game will seamlessly transist from land to sea and back again.
And the big one. Now you're on the other side of the fence:
-"So, you are now a full-time employee of Abstergo Entertainment, and you've been hired there as a researcher. You are the one in the Animus doing the research on an important character from the past, Edward Kenway."
....could be possible the new main character is a Templar (part of the same family tree of Desmond Miles) and slowly learns the truth of who he works for through Kenway and the Assassins? Interesting.