Um, no. We've repeatedly said 1 per year.
But, wouldn't that be in addition to the books we're already getting right? So, 1 setting specific book like SCAG and 1 generic book too.
Now, to be fair, 1/year probably wouldn't be a huge issue, depending on how meaty the book was. But, remember, you've shifted the goalposts pretty hard here. We ARE getting 1 book per year, just not one that you want.
And, isn't your argument that without these books, people will leave D&D for greener pastures? That without a generic splatbook every year, people will move on to games with more material. But, where is your evidence of this? Two years in and every single metric we look at shows 5e D&D to be doing spectacularly well. It's by far the most played RPG. It's by far outselling any other RPG.
How much better would it have to do to justify the expense of what you're asking for. And, remember, you're not asking for just one book. You're asking for a class/race book, right? So, which races? Which classes? How many are we talking about here? Because every book like this that you add, that add new classes, and new races and new feats and new spells, makes the game just that much more complex. Three Big Book of Classes down the road and suddenly we're back to needing a spreadsheet to track options.
I mean, the primary argument against 3pp is that they aren't Adventurer's League compatible. But, that doesn't apply to SCAG does it? SCAG material is legal in AL play. So, why isn't SCAG being included as new material? Granted, again, it might not be new material that you want, but, we're not talking about what you want, we're talking about what's good for the hobby. Volo's guide material will likely also be AL compatible. And, wasn't the online web content for Princes of the Apocalypse also legal?
So, if you're an AL player, you've had two supplements so far and a third one due in a short time. If you're a home player, then there's the DM's Guild right there with more content than you could possibly use, all for pretty much the cost of a cup of coffee. Money wasted arguments kinda fall down when twenty bucks buys you eight or ten supplements.
To sum up though, what evidence do you have that a lack of generic material is hurting the hobby in any way?