as a customer of Cd Project Red (Witcher 3, Witcher tv show.,CP 2077,. Edgerunners so includding cross-sales) I will speak only to what is official
keep players in the game = marketing tours
different marketing tours = different dates to stream live via influencers. this will enlarge release window and buy time.
combine of competition launch dates = bad idea. why? cause always be another game of the table. you are selling something additional to current players. the >10 mln of gamers want something to buy today period.
If you want to compete with Ubisoft and Bethesda go on.
but in December you will compete with legendary Stalker 2 as well and new Metro game is in development.
but if you have something to release right now or in June-July be it semi-final major patch (excluding bugfix) u have an unique opportunity to strike first, strike hard before Starfield.
but do what you want!