Today is 20th Anniversary of Half-Life 2
The game is free on Steam as part of celebration. Valve released a documentary with the original team that worked on the game for 6 years through many troubles. It does not look like we are getting Half-Life 3.
What we are going to get is a graphical improvement to the original game. It will help more people to experience the brilliance of this 2 decade old game without complaining on the graphics (which still look fine).