There's a good chance it will be.I am worried its going to be some crocodilian.
Anyway, I say this a lot, but some of the picks in this thread are utterly bonkers for the anniversary. It feels like a lot of you are looking at Frontier like it's a family friend rather than a business. The anniversary gift is an act of corporate goodwill to maintain their brand, not a gesture of altruism. Anything free will always be the minimum standard and something they don't think will sell; i.e. a species that they aren't going to put in a DLC. It's not going to be a flying bird, it's not going to be a complicated model, and it's not likely to be a species around which there is a high expression of need (so nothing in like the top 15 of the meta wishlist).
In terms of what we should be looking at, it's species that have gained a lot of discussion in the context of the anniversary. Simplistic animals that people want but wouldn't want to take up a DLC slot. The American flamingo, Nile crocodile, and even the Eurasian brown bear are potential options. I would say the European bison is another one; it's widely considered an essential European species but usually when it's discussed the general feeling is "yes but there's stuff I want more". That's where it hits the anniversary gift sweet spot; popular, not worth a DLC slot, easy to make.
Anyway we're days away, so we'll soon find out.