No, your eyes don’t deceive you: there is one more canon Gabriel Knight story, a comic written by Jane Jensen herself for the first game’s twentieth anniversary. With illustrations by Elisa Pavinato and colouring by Bruce Brenneise, you can read the whole thing here.
Given that the story takes place after Blood of the Sacred, Blood of the Damned, and coincided with the release of the first game’s remastered edition, I suspect it was written in the hopes of renewing interest in the franchise and continuing the games (the last one ended on an open note, after all).
But since this came out back in 2015 and there’s been no word since on Gabriel’s future, it would seem the attempt was unsuccessful. So let’s just enjoy Temptation on its own terms…