hawkeyefan
Legend
First, more frequent than what? The nothing put out so far? Yes. More than 1 book a year? No. Second, I have not said that I would not be enticed back by one source book. I said it would depend on how much longer they make me wait, and how much is in the book.
You said that folks would not come back for one book if they did not also have the expectation that more would be forthcoming.
More frequent meaning in addition to their approach so far. In 2016, the put out Curse of Strahd and Storm King's Thunder as adventure paths, and Volo's Guide is coming up in a few days. Two adventure paths and then a general release book (not to your definition, but this is kind of the point) in November. Last year we saw the SCAG in November.
The game is using FR as the default setting. It's baked in. You won't see a product that doesn't reference the Realms unless and until they introduce another setting. Therefore, SCAG and Volo's are the general release books that WotC has produced. You just deny that they fit that category because of your personal preference.
Hence, your desires are more specific and more demanding than the average customer. You want them to redefine what they consider a general release, and you want them to go from 3 books a year to 4. You say "it's only one book" but would you say "it's only an increase in production of 25%"? Asking anyone to do 25% more is significant.
The Sword Coast is a place in the Forgotten Realms, so it's very clearly setting specific. Volo's is also setting specific, but probably more easily used elsewhere since it consists of monsters. It really depends on how much setting content is in it.
The Sword Coast doesn't exist. It can be anything I want it to be, or anything you want it to be. There is plenty of material to be found in that book that can be used in a general way, for a game in just about any setting. Yes, the material assumes a specific setting by default, but so what? Almost all RPG books have some default setting, or implied setting.
No. 1 book a year is not a hefty expectation. They were putting out 30 books a year during 3e. Adding 1 book a year to 5e raises the number to about 7-8 annually.
I don't know if those numbers are accurate or are even meant to be accurate. But what they put out in the prior edition has no bearing on what they are doing now, except that it has influenced your expectation. Their business model has clearly changed. You don't like that, and that is of course fine.
What I find odd is that you see the idea of you adjusting your expectations on what to expect from WotC based on current evidence is the less sensible option when compared to WotC altering their publishing schedule to try and earn your business.