We've already been seeing inter-company DC/ Marvel crossovers in all but name since the early 1970's.
But it will be interesting to see how much more extravagantly they can do it, when they aren't just doing it secretly for their own amusement and hiding it from their bosses.
https://www.cbr.com/dc-marvel-crossover-easter-eggs/Writers Len Wein, Steve Englehart, and Gerry Conway were at a Halloween party in Vermont when they hatched a plan to quietly crossover the Marvel and DC universes, and even better, Englehart, Conway, Wein, and Wein's wife Glynis, would all show up in the comics as well.
It started in AMAZING ADVENTUREs #16 where Beast hitches a ride to Rutland, Vermont with the quartet. Things get rough when Juggernaut shows up and Glynis, who's dressed as Supergirl for Halloween, goes missing!
Then in THOR #207, the three men find Glynis, but just then their car gets stolen!
In JUSTICE LEAGUE #103 we find out that the car thief was none other than Felix Faust! Faust then uses his powers to take control of the participants at a Halloween parade, many of whom are dressed like Marvel heroes!
They left out one from Simonson's writer/artist run on THOR, where Thor meets (obviously, but not named) Clark Kent.
https://viewcomiconline.com/thor-v1-341/
