John de Lancie said his character is a "catalyst" this season, ergo in the margins of things. He also said he filmed scenes for six episodes, which have been spread out into five so far.
He'll probably be in the final three, as some of what we've seen has, like I said, been sprinkled throughout most of the season e.g, the end of episode 1 was filmed along with the big chunk from the beginning of episode 2 and the blink-and-you'll-miss-it appearance in episode 3 is probably an alternate take from episode 2. This leaves episode 2, 4 and 5.
And we know he's gonna be in next week's. Also, we can assume there's at least one more scene with Q and Jean-Luc... probably in the season finale.