Even if he never speaks again, we might see him, and even if we never see him again, he might still be alive. So we can’t say anyone has been killed! 
As for replacing actors, with so many years of voice samples, sooner or later we’ll get new episodes where robots do the voices. I’m not saying it should be that way, just that it will be that way, eventually.
I didn’t need more nightmares. Is this how it is on your home planet?
For me, he’s dead as we know him.
What’s more likely to succeed is not a pure robot voice but a robot-organism collaboration, as envisioned in The Diamond Age. The actor goes into a studio and says the lines, and they come out in the product sounding completely different but still clearly being steered by the actor. No matter how advanced the programming is, the discerning customer can always tell if there’s a human behind the mask, and the best actors still fetch higher wages, but they don’t need to look pretty because everything is visually augmented like nobody’s business.
Gordon Shumway? Or are you thinking of something else?
They’ve replaced voice actors before. I think they only didn’t for the ones that died IRL. In this case, it sounds like the voice actor, who does other voices, has decided not to continue. Since Apu is a popular character, I think they’ll just get an Indian voice actor to continue in a less stereotypical voice. I’m guessing the replacement will sound like Raj from Big Bang, if not fully Americanized.
George Shumway lives! 
(Well no, he probably doesn’t still live in 2020. Phil Bruns died in 2012 and Tab Hunter in 2018. Anyway, spoiler: his abduction turned out not to be his death.)