It's happened before. Marvel and DC Comics have come together in the past for big crossover events such as Superman vs. The Amazing Spider-Man, DC vs. Marvel, JLA/Avengers. So why not now? If there was any kind of big comics event that would for sure boost comic book sales across the board it would be Marvel and DC joining forces once more. Even some of the publisher's writers seem to think so. That being said, what would it even look like? Would it be a simple matchup of characters or teams? While fun, it seems like there should be something more to a new potential crossover event. Plus, the publishers may already have an idea right in front of them.
Writers like Gail Simone and Donny Cates, both writers for DC and Marvel, have given their support for such a crossover idea over social media. Their reasoning is sound as well. Simone notes that next will mark the 25th anniversary of the DC vs Marvel crossover, so the timing would be perfect. Furthermore, the boost in sales would not just be to help the comic book industry get a greater bump than their average sales (though that would certainly be helpful). Rather, given the current state of things with the COVID-19 quarantine, it would help make up for the losses the industry has suffered and will inevitably continue struggling with as the lockdown remains in effect. The crossover would definitely bring in new readers and bring back old ones as well.
One possible avenue for a crossover that could be taken by both publishers could be one that DC has already sowed the seeds for. In the final pages of Doomsday Clock, the DC/Watchmen crossover event from Geoff Johns, Doctor Manhattan sees Superman's future and future crises that have yet to pass. One such event Manhattan refers to as the Secret Crisis. Fans will recognize that it's a hybrid of names. "Secret" like Marvel's Secret Wars or Secret Invasion events, and "Crisis" as in a large number of DC events as in Crisis on Infinite Earths, Identity Crisis, or Infinite Crisis, to name just a few. This Secret Crisis is a sort of tease towards a new Marvel/DC crossover that could happen in 2030 according to Doctor Manhattan.
Manhattan also shares a few pieces of information as to what might happen in this Secret Crisis. Supposedly, Superman would get into a brawl for the ages with Thor, the God of Thunder. Furthermore, a Green Behemoth, stronger than even DC's Doomsday, would sacrifice himself to protect Superman from invaders. This "Green Behemoth" has to be a reference to Marvel's Bruce Banner, the Incredible Hulk.
The pieces are there. Fans are excited. It would help sales. Why wait another 10 years for Secret Crisis? There doesn't seem to be any reason for either publisher to not at least entertain the idea, which would no doubt prove to be mutually beneficial not just for themselves, but for fans as well and the industry as a whole. No matter how it all turns out, or even if Secret Crisis just remains a cool tease, it's still fun to imagine what a brand new Marvel/DC crossover could look like.