[UncannyGirl]

One aspect us fans need to keep in mind is the decision by Ghost Corps to intentionally move away from IDW to Dark Horse Publishing to produce the "Back in Town" story. "Back in Town" was already to be 100% cannon to the main Movie Dimension's timeline. (Let's simplify using the IDW Ghostbusters Dimension numbering system with the logical designation of: "84-P".)

While the pre-release press tour for Afterlife with Ivan and Jason Reitman immediately made the IDW timeline non-cannon to the 84-P universe. I will personally stand by the division of those two timelines as a good thing.

The IDW cannon deserves its own separate place in the Ghostbusters multiverse. It sits happily in a timeline where the Video Game happened and is the equivalent of what if the game's success led to Sony finally funding the proper third film before Harold's passing. If by chance you have not read the two main collected stories: "Total Containment" and "Mass Hysteria" (which IDW massively needs a second printing for), I would recommend them! If you're on the fence, YouTube search "Ghostbusters IDW" to find a team who voice radio'd the first nine issues!

After reading the main story in those collected volumes, I feel the 84-P timeline no longer needs to be the only timeline which gets the fans' love! Besides, IDW after the "Ghostbusters International" story started telling Ghostbusters multiverse stories.

We do need to address obvious specter of the room:
If Dark Horse has the rights to Back in Town, does that mean IDW does not have the rights to the 84-P reality?

We need to wait for that to be addressed. For all we know following "Back in Town", Dark Horse will continue to tell more tales in the 84-P reality. (IDW is a rival publisher so they do not gain anything by sharing being cannon to 84-P.)

If there's a chance that IDW does have the rights to be able to produce comics referring the 84-P timeline, I feel the only acceptable approach is another "Crossing Over" event (the essentially What If Spider-Verse was Ghostbusters-verse.) However, this time around, I would love to see it treated as Marvel has started treating Spider-Verse events where we have 3 main types of stories: the huge over arching plot, stories involving the realities of the main teams involved, and a set of stories where we get tiny tales involving countless extra realities (Spider-Verse and Venomverse did this where issues would have 3~8 small tales with each one visiting a reality.)

There's only one aspect in which I don't want to see in some 84-P cross-over tale: time travel. 84-P is now focused on a new team and generation of Ghostbusters. We don't need to see earlier points of the 84-P timeline. (Afterlife told us what we needed to know about between Ghostbusters 2 and it to an acceptable point.)

[Bison256]

I think the decision to give the license to dark horse was due to the dire straits IDW is currently in. Let's pretend IDW was solvent, I think the comics would have been rebooted/become a separate universe to the afterlife timeline. But we would have retained the same creative team and art style. Perhaps down the line there would have been a crossover where Phoebe and friends meet and work with the IDW version of the guys.

Edit: After writing this an idea came to me about how Afterlife could take place in IDW continuity in the most comic book way possible. We open in 2012 of the main IDW universe. The characters are older similar to sanctum of slime versions. The comic is a crossover between back to future and Ghostbusters. Typical crossover stuff happens, but then there's a massive pke burst in Oklahoma centered on some nowhere town called Summerville. A massive "ghost storm" breaks out engulfing the great plain getting ever larger. Somehow it's making Gozer stronger dispite being in the containment unit. It looks like all is lost, nothing can be done. Egon realizes if they had manipulated Shandor's mandela instead of destorying it they could had limited pke leakage into their world for decades, in effect reducing the amount ghosts for the next 40 years. But there's nothing can be done now.

Then doc Brown points out he and Marty have the DeLorean. Somehow the guys integrate a flux capacitor into ecto 1 and go back to 1990.(before the events of the video game) Everything goes according to plan. The video game and IDW timeline never happen. But Egon realizes he made a mistake. Gozer will now be able rise in Summerville and there be no Ghostbusters to stop it. In a panic old Egon rushes to his younger counterpart who is alone and does he best to explain everything as he's fading a way. Young Egon gets enough information to lead him down the "spooky crazy guy" road and hauntings dry up due to the changes to the mandela.

A bit comic booky but it pays off the running gag of Egon not believing time travel is possible.