Alot of us are aware of the lengthy development cycle of Doom 2016 which was originally announced as Doom 4, back when John Carmack was still at id Software at the time. Originally planned to be an id Tech 5 engine game, it later jumped to become a debute title for the id Tech 6 engine instead.
Originally announced as a Doom II-ish sequel to Doom 3 around the late-2000s, it would suffer from being a Call of Duty clone, resulting in the team at id Software referring to it as "Call of Doom" during development. By the end of early-2010s, the original version of Doom 4 was scrapped and John Carmack would leave id Software shortly afterwords.
The Doom franchise would get rebooted in the mid-2010s resulting in Doom 2016 to good reviews and resulted in the current boomer-shooter we still have today.
Given that it is very unlikely that the playable builds of Doom 4 (the ones when John Carmack was still at id Software at the time) will ever get leaked to the public, I wonder if anyone would be interested in creating a GZDoom project that would bring the Doom 4 we never got to a playable form using all the available video, concept art and screenshots, similar to the Duke Nukem Forever 2013 eDuke32 mod for Duke Nukem 3D which was made using trailers and screenshots from various iterations of that game prior to the leak of the 2001 build.
It would probably be a curiosity to be taken seriously, given that we will never see the John Carmack-era builds of Doom 4 get leaked anytime soon. Hopefully, anyone would be interested in spearheading a Doom 4 1.0-inspired project in GZDoom.