The way I see it, the big boys create games that acts as platforms and users freely create content of their own using these platforms. Bethesda/Microsoft might be in a good position to achieve this, they have good modding communities around their other games, really interested what their next title brings to the table, hope they don't blow it up like the last time they tried to monetize mods.
You also have something like Roblox, where the concepts of game development and modding kinda blend together, so it's definitely a trend to keep an eye on in the future.