It was officially announced on January 26, 2019. It is said, that it will be the first free-to-play DLC available for the game.
Further announcements suggested it should be available in 2019, although developers' time issues and several technological problems caused it to be moved to 2020. The official release date is still unknown to this day.
Global Rivalry will contain 180 new companies - 15 companies per branch. 13 companies are pre-set companies, like the ones in the standard, vanilla game. The other two are custom companies, that player will be able to set information about - including the name, home state, as well as starting modifier! The companies editor will be available in the main menu, right after picking the single player game. Players have more control over the situation now...
This DLC will also include new, extra mechanics. Global Rivalry will include Stocks and Global Investments.
Stocks are a way to invest in different companies, not taking a part in the game, called Stock Companies. There are 5 Stock Companies from 5 different branches. Their value in the market depends on various things happening during the game, such as events effects, companies' purchases and specialists upgrades. They directly affect the Stock Companies' values and their downward or upward tendencies. Whatever you will invest in, you can buy more stocks or sell them whenever you want.
Global Investments are a way to quickly spend your money. For a big prize, they will give you a lot of extras and positive effects for given amount of time. It is a good tool in the late game, when a lot of money is just laying around and could be spent on something else.