Too small, plus it would require a lot of work because we don’t have any habitat animal that small.
Some of the larger species are bigger than meerkats, but I think the bigger issue here is that there's nothig for Frontier to make it out of.
The anniversary animal is not going to be some super-unique new species nothing like anything yet in the game. It's always going to be something fairly basic and low-demand like the ruffed lemur and red deer. It won't be marketable in a DLC. For example, it definitely won't be the...
It's an exhibit animal, for one thing, and regardless of
what the exhibit animal is they aren't super popular, and Frontier knows this. Secondly, the brown-throated sloth is a DLC animal that didn't come out that long ago, so they won't give away for free one of the big selling points of a DLC (especially a recent one - and again, the red deer is not an exception, whether it was made out of the fallow deer, reindeer, or even another animal, deer are not big sellers). Thirdly, aside from the butterflies that were deliberately made to share space (and thus share the same animation cycles to avoid collisions), each WE animal has a unique exhibit set-up, even between the two fruit bats AFAIK. That's more work than they'll give away for free.
As usual, people are setting their expectations way too high with this.