CDPR writes:
Orion is a codename for our next Cyberpunk game.
Polaris is a codename for the next installment in The Witcher series of games.
Canis Majoris is a full-fledged Witcher game, separate to the new Witcher saga starting with Polaris.
Sirius is a codename for the game developed by @molassesflood , set in The Witcher universe and created with support from CDPR.
Hadar is a codename for a third, entirely distinct IP, created from scratch within CDPR.