The most obvious sign that Liverpool have already won the title is that bookmakers are not accepting bets on it.
As for next season, it will be a different team - Arnold will leave, Salah may leave, Van Dijk too, etc. It's too early to talk about next season as we don't know what kind of team Slot can put together plus we don't know what the competitors can do.
If I've failed once, twice, then thrice I don't think I'll want to fail the fourth time, that's exactly what Liverpool people should do after losing in the Caraboa Cup finals to Newcastle, they should recover quickly from their grief and train harder to retain the 1st place for the remaining games and win this season's Premier League trophy, that's their only chance of winning a trophy this season and if they relax about it they could lose that opportunity to Arsenal, they're lucky that the break is by the corner and it's enough time ease their pains and I'm sure that they'll be fully fit and ready to end the season in a very good position instead of failing again like they've done in other competitions, Slots still got some work to do on those boys in the dressing room, they need to be motivated with words and not just training and drilling alone. Too bad Liverpool would lose some key and experienced players after this season it would be tough if they don't find good replacements for the against next season.
Although I think Liverpool are not in any danger (12 points is too much for the remaining 9 games) but from a purely psychological point of view Liverpool are really lucky that there are now national team games. The players can take their minds off two painful defeats in a row and then start all over again. By the way, the first game after the break promises to be exhausting - Everton is a fundamental rival and they have two whole weeks to approach the game with Liverpool in maximum shape.