Booot achieved a draw against Houdini and Ginkgo achieved a draw against Komodo! Therefore Stockfish's potential paths to the final have increased; for example, if Stockfish can beat Houdini and draw against Fire, while Komodo beats Houdini, then Stockfish would be in the final against Komodo. Or if Houdini defeats Komodo and Stockfish wins against both Houdini and Fire, Stockfish would be in the final against Houdini.
Edit: But now I'm not sure of the original comment that only the two top engines from this round will go to the final; in previous years there were more rounds before the final, but I don't understand how many of the rounds have been eliminated this year.
People in the TCEC chat definitely seem to agree with the interpretation that only the top two will go to the final.
It's kind of down to the wire now: currently Komodo and Houdini lead Stockfish by exactly one point, while Komodo is playing Houdini in the final game for both of them. Stockfish has exactly one game remaining (against Fire).
In order to reach the final, Stockfish needs to win its game against Fire, and also Komodo and Houdini need not to draw. Then Stockfish would be tied with whichever of Komodo and Houdini loses the current game, and I guess there would be a tiebreaker prior to the final.
If Komodo and Houdini draw now, they're both guaranteed to face each other in the final. People in the TCEC chat are pointing out that if they were human players, they would face a strong incentive to deliberately play for a draw or to accept one if one were offered. But presumably the software has no idea of this!
Edit: But now I'm not sure of the original comment that only the two top engines from this round will go to the final; in previous years there were more rounds before the final, but I don't understand how many of the rounds have been eliminated this year.