We have no way of knowing what the next xpac is, until it is announced. I'm sure it will be easier to guess, the closer we get to 5.0, but as of now it looks like it could go one or more of many different ways. 1. A Bukyo Expansion, where we deal with Hingashis attempt at reform. The caste system is apparently a huge problem, leading to civil unrest. 2. Garlemald. Obviously that Garlemald Embassy has to be set up for later. We're also at war with them. 3. Thavnair. Out of all the other known nations, we get a Thavnair embassy, plus it's on the map. It's very possible. 4. More of the east opens up, allowing us to travel to Naxcia, The Burn, and more unreleased places. 5. Sharlayan opens up for some reason. 6. The Roe origin land of Aerslant. 7. Meracydia.