To be fair, he never went away. Writer Warren Ellis has been finishing off The Batman's Grave with Bryan Hitch, which recently concluded its twelve-issue run. He's also been working on the fourth season of Castlevania for Netflix. But after a series of allegations were placed against him over the summer by dozens of women and non-binary individuals, and despite their statement that he should not be "cancelled" for any of this, several projects were cancelled by co-creators, he withdrew from a few work-for-hire projects himself, and a couple of companies dropped certain publishing projects.
I have stayed in touch with Warren Ellis, and two days ago he gave a small mini-announcement that he would, at least be returning to some form of digital media outlet, resurrecting his mailing list Orbital Operations, stating "Warren Ellis newsletter ORBITAL OPERATIONS planned to resume in 2021 as occasional missive. Subscription link in bio." And indeed, there it is – http://www.orbitaloperations.com/
Warren Ellis is best known as the co-creator of several original comics series, including Transmetropolitan (1997–2002), Global Frequency (2002–2004), and Red (2003–2004), which was adapted into the films Red and Red 2. Ellis is the author of novels Crooked Little Vein (2007), Gun Machine (2013), and the novella Normal (2016). He has written several Marvel series, including Astonishing X-Men, Thunderbolts, Moon Knight, and the "Extremis" story arc of Iron Man, which was the basis for the film Iron Man 3. Ellis created The Authority and Planetary for WildStorm, which radically affected superhero comic book storytelling for decades and directly included the look and tone of the Marvel Studios movies. He co-created comic books such as No Heroes, Black Summer, Doktor Sleepless and Anna Mercury for Avatar Press. He wrote the video games Hostile Waters (2001), Cold Winter (2005), and Dead Space (2008) and also wrote the animated TV movie G.I. Joe: Resolute (2009).
Warren Ellis is also well known for sociocultural commentary, both through his online presence and through his writing, which covers transhumanist (most notably nanotechnology, cryonics, mind transfer, and human enhancement) and folkloric themes in combination with each other. What he wants to say now – and who will want to listen to him – well, that's being reserved for 2021, it seems.