What do you want to see?
Personally I am looking forward to expanded options for Cardassian ships and introducing other factions like the Tholians and Breen.
Also official artwork has many Caitians but no stats yet so I’d be very surprised if they were not included.
Tholians, more federation races, Cardassians.
I’m contemplating a Cardassian War (missing years; post TOS movies well before TNG series).
Having expansions on the Cardassians, Breen and Tholians will definitely be appreciated to expand the range of antagonists.
Are the Nyberite Alliance based in the Alpha Quadrant? They’d be interesting to see as its implied to be open to outside races being members of their military. Could it be a Foreign Legion type ideal there or is the Alliance multi-species and open to others similarly to the Federation?
And also the Tamarians as well (the ones in a TNG who had a brief war with Starfleet and an officer adopted a human boy) just to get a feel for that conflict as well.
More Federation races will be good to see as well. In general it kind of feels like the Beta Quadrant saw a lot of the Federations 23rd Century history and the Alpha Quadrant sees more of its 24th Century history, at least to me.
Seconding Caitians - also Edoans! (As seen in the Command book.)
You mean the Talarians.
But yes, I would like to see Talarians and Tamarians.
As for playable species, there are too many to list. But Aenar, Caitians and Saurians are among them. Also maybe Barzan since they are featured currently in Discovery.
Dangit! Yes, the Talarians 
too many similarly spelled names! Though you’re right, the Tamarians would be interesting to include.
Aenar would have been covered in the Beta Quadrant book if they are keeping them in the proper quadrant.
I also am looking forward to the cardassian content. Breen/tholians etc that have already been mentioned will be great too. Caitian stats are a must.
I’m not entirely sure which quadrant a lot of things would fall under, but I’m hoping we get some love for the Suliban at some point in one form or another.
I’d also love to see something unexpected - always nice to have a surprise inclusion.
I believe the Suliban were in the Beta Quadrant, so they most likely will not be in the Alpha Quadrant book. If they ever did era books, I could see them being included in the ENT era book.
I would definitely like to see more playable federation species covered in the book, but I believe it was mentioned that they would be covering the Cardassians, DS9, and the Maquis and Ferengi alliance in this book.
But don’t quote me on that… 
I want Catians, Edosians, Saurians, and Takarans.
I, too, am finding myself in need of a Barzan writeup all of a sudden.
Technically, Aenar aren’t a distinct species. They’re a rare psychic subspecies of Andorian, easily represented by adding the Aenar Trait to an Andorian character (which includes their blindness), and taking the Telepath talent (yes, it’s a Betazoid talent, but that’s why most of those talents have “or GM’s discretion”).
Aren’t the Aenar covered by Continuing Mission, for a temporary fix…
If the Alpha Quadrant book follows the same basic organization as Beta, I’d expect the longer writeups to be the Cardassians and Ferengi. Beta covered the Federation, so maybe there could be a third long writeup for the Bajorans. Tholians, Breen, and Talarians are all candidates for four-page writeups comparable to the Gorn and Orion sections in Beta.
So far, PC species writeups have been species with at least one representative in Starfleet, so I won’t be surprised to see both Caitians and Edosians. Maybe the Ferengi writeup will be reprinted from the DS9 characters supplement, but any of the bit-part species from the TOS movies could also turn up.
I for one can not wait for it.
Wish it was July already.
I always liked the Anticans and Selay. They have an interesting dynamic.
Also, please include the Prometheus class! 
The Beta Quadrant book didn’t include any Starfleet ships, and I don’t expect Alpha to change the format significantly.
Agreed. If it follows the Beta Quadrant model, we should see a significant number of species added to the game, but not spaceframes.
I’m expecting Tholians, Cardassians, Ferengi, Breen, more Maquis stuff, and some information on the Badlands or like… Bajor.