I'd say it's not a big stretch at all.
Tsukiyama calls him "Kaneki" in Ui's presence; he had to be silenced before Ui could make the revelation that Kaneki had regained his memories.
In the double page where he impales and suspends Tsukiyama in midair, a series of smaller panels illustrate Kaneki first glancing at Karren; the elipse "..." panel is Kaneki contemplating whether Karren is physically capable of intervening, and is adjacent to the panel where he next glances at Ui's silhouette (note the katakana in that panel) before tossing Tsukiyama overboard.
I would love to see the Japanese raw for the page where he farewells Tsukiyama - to confirm whether he uses "Sayonara" (as a final goodbye) or "Mata ne" (as a temporary parting). That might reveal more of his intentions.