As of now, there are no confirmed plans for Marvel Cinematic Universe (MCU) and DC Universe (DCU) heroes to appear together in a movie. Both franchises are owned by different companies—Disney (Marvel) and Warner Bros. (DC)—and have their own distinct cinematic universes.
However, crossovers are not entirely impossible. Marvel and DC have collaborated in the past in comics, such as the Marvel vs. DC series and the Amalgam Universe. Fans have long speculated about a similar crossover in movies, especially given the massive popularity of both franchises.
Key challenges include legal agreements, profit-sharing, and creative control. If such a crossover were to happen, it would require unprecedented collaboration between the two studios. Directors like James Gunn (who has worked with both Marvel and DC) could potentially facilitate such a project in the future, but as of now, it's more of a fan dream than a concrete possibility.