There will be stuff shown when it is ready to be shown.

As a general rule, games are announced without a lot of detail. While some games are announced late in the development process, sometimes it can be years with only an occasional bit of news or screenshots, etc. Then information starts being released leading up to the game's release (or sometimes there are delays, engine changes, studio/publisher issues, projects cancelled, etc).

Dragon Commander and D:OS were confirmed to be in development but only referred to as Project D and Project E for some time, with little detail provided. While there were some periodic general information mentioned (and screenshots posted of a test area made for the game engine, etc), the names and more detailed information took 7 months and 16 months, respectively.
Beyond Divinity and Divinity 2 were similar.

For BG3 the announcement was included in the Stadia announcement, and kind of needed to be mentioned before Baldur's Gate: Descent into Avernus. However, it's not like it could have been delayed much longer, even if that were not the case: there were already rumours of the game's development and a previous leak (though a third hand source, so it didn't gain much traction at the time) that was starting to get more corroboration.