Well I'm sure they announce it early because it's not for us, it's for the investors. But I think there is a downside, announcing it too early with like a CGI trailer puts it in the news and gets it talked about, but gamers develop an "vision" of how the game might be and you end up with a product that will definitely disappoint a lot of people. I'd say cyberpunk was one, due to the announcement time and what they actually showed it was hyped to the moon and back (people talk about games so they just started assuming).
If you look back on it now, people's expectations and ideas of what the game was going to be were very different than what the product ended up being (besides the bugs). I would rather get the game announced with real fucking gameplay.