Artifact Will Not Die. Valve is Working on Artifact 2
Valve didn't abandon Artifact. According to Gabe Newell, the developers are working on a complete re-working. The changes are to be so serious that among the developers the project is called Artifact 2.

Gabe Newell's Artifact is a "giant disappointment" can be read as a death sentence for the card game from the creator of Magic: The Gathering. This, however, was denied by Gaben himself. In an interview for the Edge magazine (via GamesRadar), he talked about how Valve was surprised by the game's failure, and repeated the thesis that it was necessary to draw conclusions from this lesson. This lesson is not to be applied in some future game, but in Artifact 2.
While not the game's offcial name, that is the callsign of the project among the devteam. It will probably not be a continuation, but a "version 2.0", like Half-Life: Alyx.