If Universal gets a third park, I imagine it would just be IOA 2.0. More areas themed off IPs, except probably with a different packaging device then "islands" and/or "adventure". For example, if the main areas end up being based off Fantastic Beasts, Zelda/Pokemon, Universal Monsters, Back to the Future/Jaws, and Lord of the Rings, then it could be time travel themed or something, as all of those (except arguable Pokemon) take place in the past.
Also, out of the blue timeline prediction:
2016 - Universal officially gets the land, land breaking begins.
2017 - Construction fully begins, and ffficial announcement, with only a small amount of information such as IPs, location, etc.
2018-19 - Nothing, besides rampant construction.
2020 - CityWalk District 2 opens, WNW plot's TTC equivalent opens, a few of the new hotels open.
2021 - Park opens.