While I am looking forward to seeing Captain Marvel in Avengers 4, I do hope she doesn't have too big of a role in defeating Thanos. This has been built up for so long, I wouldn't want someone just been introduced at the last minute as a bit of a deus ex machina.
They won't be so stupid, that would be like having Superman coming at the last minute to bitchslap the villain, while smiling, and the rest of the Justice League just looking at him