City have proven two seasons running that they're of the quality to hit 90+ points. I have no doubts that next season will any different.
Liverpool have done something incredible this season, however, I see nothing to suggest that a squad with inferior quality to City will replicate this seasons form going into the next to the degree in which they have this season. What they're doing with this squad is unsustainable. We all know it.
Next season's going to be an interesting one.
As you say, City seemingly have a machine capable of putting 90+ points on the board season after season, which should be a comfortable league winning margin. The closest a team has come to 90 points and not won the league was us in 2012 when we lost it on goal difference with 89 points. Should City stutter, and Liverpool win the league, it'll be interesting to see how their squad reacts in the new season. The illusion may have been shattered, and they could all still be scratching their heads wondering what happened. After all, I doubt they planned to still be in a title fight at this point of the season. It was probably supposed to have been all wrapped up a few games ago.
Liverpool may face a similar problem should they not win it, but with much more historical weight to compound it. Having gone so long without a title, to potentially record the third highest points total of any Premier League side from any season ever, only losing one game across the whole season, and still not win the league could be catastrophically demoralising. To fight so hard all season and end up empty handed could be a killer for morale.
I think there's also the potential for at least a temporary Liverpool drop-off next season even if they win it. The long wait will finally be over, and there might be an element of "mission complete" as they head into the new season. I think City suffered from that in 2012/13, after winning it in such dramatic fashion the season before, winning just two of their opening five fixtures that year.
Of course I could be way off, and if City lose it they'll just put 96 points on the board next year anyway, and whatever happens with Liverpool, having shown such remarkable resiliency and an almost inhuman ability to keep their key players fit, they may well do the same, regardless of whether they head into next season as champions or arguably the most unfortunate runners up ever.