Naaah. They're certainly at a point in their careers where they're thinking about what it means/takes to keep on being The Chemical Brothers, but I don't think Direct Buki is some orchestrated attempt to cleanly close the curtains.
I don't think they're planning to step down soon, rather, they're just uncertain about what else there is to say, and that could mean anything from 20 more years of the Chems or a farewell by the end of the tour.
Ed's current situation reminds me of Karl Hyde's, from post-Oblivion With Bells to today. If you watch interviews of him ahead of Barking he talks a lot about friction between him and Rick and how working with someone for so long caused the whole Underworld thing to lose its charm. Later, skip to his "solo" material and he talks about loving doing his own thing and stepping away from being "that Underworld guy on stage, etc", and this continues with the two albums he did with Eno. Finally the Dubnobass remastered tour comes along, and particularly in that BBC show they did you can hear how much respect Karl had regained for Rick in his absence, almost apologetic at times, really praising his work behind the synths. It took time away to re-realize why he's doing what he does. And though the Ed/Tom thing's not an analog for Karl and Rick's three decade partnership, I feel like Ed's in a similar doldrum. And he's not out of it yet. But after these years of passionately working on scholarly work entirely his own, maybe rejoining the tour in the fall will light that Chemical spark again? I hope so.
Never for money, always for love.