The Marvel Cinematic Universe typically plays out in real time. The only notable exception is Captain America: The First Avenger, which was set during the events of World War II; otherwise all films have so far been generally set in the year of release.
Back in November, director James Gunn's brother Sean confirmed that Guardians of the Galaxy Vol. 2 would be breaking from this tradition and picking up "only a couple of months after the first movie". The director himself later revealed the main reason for this was to allow Groot to still be in his baby form, but that doing so changed how he approached the movie and the characters. Now we have some details on how this decision has impacted the film and where exactly the sequel will pick up.
When talking to Kevin Feige on the Guardians 2 set last April, Screen Rant asked about what has changed between the two movies. The super producer explained how the team's developed and confirmed what we'll see in the opening sequence:
"I think they’re giving it a shot at being more organized heroes. They are, they are available for do-gooding, so to speak. It doesn’t always go well, but they try that. And when we first meet them, in the beginning of the movie, they’re on a place called Sovereign, where they’ve been asked to help with these, this giant sort of inter-dimensional beast that comes out and eats their batteries, their power source, and wreaks havoc on the planet, and the Guardians have been asked to come in and dispatch with that thing, and that’s how our film starts, and their legend, and their mythology has grown and spread throughout the universe, because they defeated Ronan and because they were able to hold, Peter, in particular was able to hold an Infinity Stone and not die, which also has spread his legend."
The sequence Feige talks about is the one that formed the basis of the teaser trailer from last November, with the gang going up against a giant tentacled monster known as the the Abilisk. This will probably be an in media res re-introduction to the team on a mission, establishing the developments Feige discusses through action. If so, that really highlights how spoiler-lite the marketing has been - even after the Super Bowl trailer not much of the actual plot has been revealed (and there are only three months until release).
Although it was primarily done to have Baby Groot, the shorter between-movie timeframe sounds to have allowed the sequel to better define itself; the new film picking up in this immediate explosion of the team's notoriety will maintain the core relationships between the characters and see their struggles as the Guardians "legend" grows, instead of having that all happened off-screen.
Regarding the opening sequence, we also asked Feige about the design of the Abilisk and whether it was a nod to anything from the comics, possibly the Cancerverse, to which the producer said "Not specifically. We don’t talk about that. It’s more just a fun beast for them to attack in the opening title sequence."
