I'll second a lot of the thoughts that were already brought up in this thread: it really depends on how much longer support will continue for the game.
If we get DLC packs until 2026 or so, I would gladly welcome at least five more cats to the game, and possibly even more. But since that most likely won't be the case, the amount of cats I would appreciate over other, more unique species is relatively low.
Obviously, any leopard is the most requested species at this point, and I would personally be very happy to receive the Persian Leopard because they would help fill a geographical region that has not been explored sufficiently by the game yet, as opposed to an Indian, African or Amur Leopard. (The Amur Leopard would be great for conservation and realism purposes, but two leopards are rather unlikely given how many different cats we could still receive.)
Then, when it comes to smaller cats, there are a couple of species that are still very highly requested, those being the Caracal, the Serval and the Ocelot. I would be happy with all three of them: the Caracal because, again, it would add to the Middle East roster and would provide a suitable alternative to the Eurasian Lynx; the Serval because it's absolutely beautiful and would be such a striking and wonderful addition to any African-themed area, and the Ocelot because it would be such a welcome alternative to the Jaguar in South American sections.
But, as for less popular species, I would also love to see a Jaguarundi (they're so beautiful, and look almost mustelid-like), a Sand Cat (they would fit perfectly next to Fennec Foxes) and, of course, the Pallas's Cat simply because they are so interesting and would fit perfectly into any Himalaya-themed section. I would even be happy with the Geoffroy's Cat, but understand that they are less highly requested. I have also seen mentions of the Fishing Cat, which I think would have made a perfect fit for the recent Wetlands Pack.
More lions or tigers are definitely lower on my wishlist, and if anything, the Asiatic Lion and Sumatran Tiger are only so requested because the subspecies choices in the base game were so off. In summary: the one cat that I truly desperately still want to see in the game is the serval, and if I could choose a second one (depending on how many more DLCs we get), it would probably be a caracal before any of the true leopards.