MCU: 10 Marvel Characters Who Will Definitely Die In Phase 3
3. Groot
Why He Has To Die
Because it's what he does.
Like it or not, dying is sort of Groot's superpower: he's the most protective of all of the Guardians Of The Galaxy and by virtue of his regenerative power, his sacrifices (though emotionally devastating) are very functional.
Sure, it's happened before to great effect, but if you're looking at Baby Groot and not thinking this more impulsive, more disobedient little rascal wouldn't do what his full grown self would ten times over, you're probably not thinking straight.
When It'll Happen
In Guardians Of The Galaxy Vol 2. And maybe also Infinity War. Possibly in every film he appears in, actually.
How He'll Die
It won't last, of course, but expect him to die again while saving his team-mates - unless James Gunn spins it for comic effect this time and makes him explode when he runs off with that bomb seen in the trailers?