President of Animal Kingdom
Most of our mammalian friends age up rather quickly compared to humans. And this is even accounting for stretching or shrinking the lifespans in comparison.I don't disagree with you per say. Developmentally he's more on order of 16-18 months. His receptive language skills imply 2-3yo. He's toilet trained seemingly? His ambulation puts him around 2 or a bit younger, but some of that may be the frailty of his species body. Some of the force stuff confuses things mobility wise.
He SHOULD NOT age up. Not out of laziness or marketing, but it would ultimately be consistent with the longevity of the species. Humanity takes an inordinate amount of time to reach maturity and I would expect a theoretically more intelligent species to take longer.
All of which is to say that absolutely all of his developmental markers would suggest he is on the precipice of speech. I actually do think he is late to speech based on his attributes in the show, maybe the trauma theory has some merit. So they either may or may not choose to have him start speaking. Once expressive language starts though it should theoretically progress quickly over a few years, even if his body doesn't really follow.
Baby Yoda has always been a bit of a misnomer from the public, he is very much acting like a toddler.
E.g., most herd animals are up and walking the day they are born.
Humans, by comparison have a very lengthy period of prepubescent development of near helplessness for a big chunk of their lifespan.
If a cow can live for 20 years, and humans for 80, then we would expect human children to be walking on their own by their 5th day of life if development scaled linearly, which it obviously doesn't.
So, how do non-human species develop in relation to humans in the Star Wars universe? No one knows.
Grogu's species could be in the pre-school stage for 30 years or 200 years... we don't know.