We occasionally see multiplayer-focused games go free-to-play when they underperform. Evolve and Battleborn are two recent examples; publisher 2K Games eventually made them free when it was clear that residual sales had dried up, both in an effort raise the active player count and to earn some cash from in-game purchases.
The timing is odd considering that Brink originally released in May 2011, but the way this game is generally regarded makes things even more confusing. Brink launched to a largely tepid reception, as reviewers mostly agreed that it never fully made good on its ideas for movement-based combat. It looked cool in a way that it couldn't deliver on.
The question attached to Brink going free-to-play is: What does Bethesda have up its sleeve? Publishers rarely give a product away for free without an ulterior motive, even if that product is six years old and incapable of driving revenue anymore. Is there some sort of Brink resurgence on the horizon, maybe via a sequel? Is the free-to-play version planning microtransactions in the near future?
Regardless, the free-to-play route is already working to some degree. At time of writing, 343 people were playing Brink. That might not be a particularly impressive number compared to other Steam games, but it's the most for Brink since July 2012. Improbably, this fast multiplayer shooter is back from the brink of death, even though many assumed it was already long dead.