I read a while back when the next gen news brought with it the talk of cloud servers supporting online games. There were rumors and hints that these servers could support multiple platforms and that they would be able to communicate with each. This rumor was nothing more than some guy quoting another guy in the comment section of a blog (hardly reputable).
Over the months though cloud servers have grown in popularity. It's been said that developers can now support iOS and Android in the same games so you can compete with friends regardless of their phones operating system. This is a far cry from the demands that console gaming would require but the general concept is the same.
I'm not saying the next Call of Duty should feature both Xbox and Playstation players in the same lobby, but I think it's time that the research gets underway. This would obviously take years to figure out and implement. If any franchise is to pull it off it would be my guess that Activision and their team of engineers would be the one to do it.
Despite Call of Duty's ups and downs this franchise still manages to support even the oldest of games, their revenue is unmatched, and they are the most popular game in video game history. I feel that with the right amount of motivation and determination, what was once thought impossible could be reality; a joining of Playstation and Xbox together in the same game.