So, the 2024 books are about 2 years away, and don't have that much bearing on this year's products as such: I'm sure we will hear more on that in the next year and a half or so.
If we look back on the past couple years of history, here is how UA timing has worked out (Nota bene that past performance does not necessarilyreflect future results):
- from 15 August, 2018 through 13 July 2020, we saw 14 UA articles for Tasha's Cauldron of Everything, which was announced in late August of 2020 and released in November of 2020. So up to a year before the product announcement, and as close as a month before the product announcement. Still, everything was tested and done before we even knew there was a product.
- 5 August 2020, we got the Subclasses for Ravenloft, which was announced in February 2021, and released in May. So, six months from the plsytest go an announcement of the book.
- 26 October 2020, we got the Fizban Subclass UA, which was announced in July 2021 for an early November release. So, q0 months before the product was announced, and a year before it was released.
- 26 January 2022, Ravenloft Lineages, a month before the book announcement, and 4 months before release.
- 11 March 2021, Folk of the Feywild, including content for Strixhaven which was announced 3 months later in June, and released 9 months later in December, and also material for Monsters of the Multiverse intended for Christmas, later January 2022, release.
- 14 April 2021, Draconic options, including material for Fizban's being announced 3 months later, released 7 months later, as well as material for Multivers in the Holidays
- 8 June, they let Strixhaven out of the bag for release in 6 months, though this material was largely cut.
So, first of all, we can see that they re pretty flexible with how often they release UA, and when. Additionally, we see that there is a shorter turnaround for Race options
The most recent UA was pretty blatantly for a Spelljammer product, probably a Setting book, which we can reasonably specualte will come out 4-12 months after the UA if it tested well, so sometime between the Critical Role book and November-ish. We can also see that a year ago, there was only one UA of 6 total released yet, so there is plenty of time for more coming for 2022 products.