It looks like the landbridge between Ilsabard and Othard is mostly The Burn, which doesn't lend itself well to (interesting) zones. The landbridge between Isabard and Aldenard though looks like it has a lot more countries in it. I could see SE making some of those countries "lead in" zones to Garlemald which is where the majority of the Zones are.

The other location that stands out is Sharlayan. Alphinaud isn't just a nobody; he's a member of a Sharlayan noble house practically speaking. If/when his disappearance gets found out would make for a logical time for more Sharlayan parties to get interested with what's happening on in Aldenard. Their big fear that Aldenard would get taken over by Garlemald is certainly not happening now. Meeting some more Sharlayans that aren't the Scions would be interesting.