Me and a friend were discussing some things... and it got me thinking. 2.4 will be the next main story portion I'm sure, and we're closing in fast on patch 2.5 right after that as such (Which is a major milestone version.) So, we were thinking of things that could happen:

1. Ishgarde could be sitting atop Alexander, an elder primal being controlled by the Archbishop / Holy See. It could awaken at the end of 2.5 in a major cutscene akin to the quality of the end of 1.0 (Due to 2.5 being a milestone patch to 3.0)

2. At the end of Patch 2.9, we could have an ascian be killed for the first time, its ashes unlock the power of flight in a chocobo, which then breeds with others to make more.

3. Square Enix likes to do things in 8s (According to my friend) So we'd have 6 primals under our belts after Shiva... which would mean 2 more. See number one above.