I also expect him to be around for a while, I just really hope he isn't. Like, if in 5.2, Elidibus just said "I have no need for you anymore, sword boy" and killed him, I'd be more than okay with that, because if 6.0 is going to be a Garlemald expansion, I'd prefer a focus on new characters or on the Ascians themselves. I liked the direction they were moving in during 4.X in regards to what post-Zenos Garlemald would look like with the Varis stuff, and I feel like 5.0 just fucking did a 180. Post 4.X, Zenos should only have been a handy puppet that Elidibus uses for a bit. The story contrivances needed to keep him in are tiring (although they've always kind of been tiring, though, he's a dude that's very good with a sword). Y'shtola needed qualified and powerful people (Kan-E-Senna, Emet-Selch) to pull her ass from the lifestream but Zenos can do it apparently by himself just via bootleg Echo. God, Y'shtola, are you even trying?
He was a cool villain for one expansion, but it's time to move on. Emet-Selch was even better villain than Zenos but I'd be even more pissed if he came back too