Urriak Uruk
Gaming is fun, and fun is for everyone
Cormyr has cities so if the use of the word town is important as you think, then Cormyr doesn't fit.
Having finally listen to it for myself I noted several things.
1. He said he's doing three things right now and at least one is an Adventure, one has the text done, one is in second draft, and the third is just starting, I think they could be all for this year.
2. He briefly mentioned in connection to the Adventure I think a minor Gazeeteer he'd done, which suggests that the AP might be the one with the text finished.
3. He later on mentions that he is currently working on a Gazetteer with multiple sections. He mentions doing towns with this section with stuff like leaders, militia, heraldry, comfort ratings and RIVALS towns, which these towns aren't apart of the same nation! My first thought when putting all this together was Zendikar, but there aren't that many towns in the setting to have major rivalries, so my second and much better thought was he is writing a section on Chessenta, it's towns/cities have huge rivalries with each other, each city/town has it's own leader, and their own seperate Militias, and because they are cities/town states they could have their own Heraldry.
The only issue is that Chessenta is the Forgotten Realm's Greece, although with Mesopotamian/Canaanite/Egyptian elements, so I don't see the book being just Chessenta because that would step on the toes of Theros, hardcore, so a FRCG/Sea of Fallen Stars is a distinct posdiblity.
Another possibility is ten towns, which do have rivalries in an AP designed to tie in with Dark Alliance which is coming out this year, although I really, really hope I'm wrong as it's my least favourite part of the Forgotten Realms, and another AP for the Swordcoast is upsetting. But it's a distinct possibility sadly.
I'll reiterate that I don't think it's Cormyr. I haven't seen any other hints to it, so I don't think it's likely.
Here's what I think the gazetteers are; I think Welch's book is a collection of adventures, set all over the Forgotten Realms. I think every adventure is set in a different location, and that for each location, there is a gazetteer. What the locations are I have no idea, but they are probably a collection of towns, cities, and other settlements.
Either that, or I'll guess this is for the Outlands.