This was announced in a very short teaser trailer (embedded at the bottom of this story) which indicates that this partnership will be centred around the movie Minions: The Rise of Gru which is slated for a 2020 release.
While LEGO sets do usually precede the movies they’re based on by a few months, the sets based on this specific film will also be out some time in 2020.
Right now there’s no details at all about what kind of products this venture will create. As with Overwatch before it the community has been creating their own versions of these characters in the brick before any official products existed. As such it’s a good idea to look to that franchise to see what we may get next year.
If we had to guess we doubt this will produce anything special outside of some specialised new moulds for the various characters.
One final point worth noting is that you may have already seen building block sets based on the Minions franchise before now. That’s because Mega Bloks (later rebranded to Mega Construx) previously had the rights to make buildable toys based on the movies.
The two companies swapping and fighting over properties like this is nothing new as a few IPs have made the switch. Teenage Mutant Ninja Turtles, for example, left LEGO a few years ago for Mega Construx. Other properties, like Marvel, made the reverse decision like Minions have now.
— LEGO (@LEGO_Group) June 3, 2019