As important as it would be for Liverpool to secure a top four finish, if they're somehow usurped and finish fifth, they'll probably be okay.
Their project is a long-term one, and another year without Champions League football won't make or break them. Arsenal haven't missed out on Champions League in decades, but in this case, missing out on the top four could actually be better for their future in the long term anyway. That leaves Manchester City, and they're absolutely the team with the most to lose here. With a huge stadium to fill, a number of below-par players (for Guardiola's standards, at least) and one of the most ambitious projects in the world game, missing top four would be a disaster. City need to qualify. The good part is, they're in pole position, and they could go on to qualify with just a draw against Watford in their final match. There's plenty of optimism that they'll go on and close the season out on a high.