There has been no official word from Valve regarding "Half-Life 3" although it was previously reported that the company may no longer be prioritizing the game's development. But according to a Reddit post that an alleged ex-employee from Valve posted last month, the game is still scheduled for release some time between the fourth quarter of 2017 and the first quarter of 2018.
According to the alleged former employee's post, "Half-Life 3" has been pushed back as the company is instead prioritizing the next "Left 4 Dead" game. The said poster also states that the company is waiting for the hype to die down before they make any big moves to speed up development and release the game.
However, the Reddit user also explained that "Half-Life 3" is no longer in active development and that no build of the game has been released for testing purposes.
"Half-Life 2" was originally released back in 2004 with its final installment, "Episode Two," having been released three years later. Following this, there have been no official releases in the "Half-Life" franchise and no confirmation that "Half-Life 3" is ever going to be rolled out. As pointed out in the previous report, Valve allegedly has no plan to shift resources to develop the game as the company is already making profits from Steam and other IPs such as "Team Fortress 2."
This could mean that whatever has been developed so far may have been scrapped and the developers will work anew once the project is prioritized, or Valve might have simply shifted resources to focus solely on "Left 4 Dead 3" while "Half-Life 3" remains in development limbo as an unfinished product that may be continued later on.
As pointed out in a report from Latinos Post, there is no verifiable evidence to support the Reddit poster's claims about previously working for Valve or the development status of either "Left 4 Dead 3" and "Half-Life 3," which means the information should still be taken as a mere rumor at this point until further clarification from Valve is announced.
