Liverpool beating Arsenal doesn't mean anything in the grand scheme of things for the short term, because lets be honest Liverpool will lose a game too, it's possible for them to go unbeaten but I doubt it, they will lose, and Arsenal can cover that difference.
That assumes Arsenal will win whenever Liverpool loses. I think last season or the season before that shows that Arsenal struggle to close the gap when it matters. They need to win every game to make sure they can win the title. Being complacent and believing that your competitor will slip up because you did is not really good. That being said, I think this applies to every team, not necessarily Arsenal only.
First no team can go unbeaten again in the English premier League no not again not even now that even the underdog teams are growing to even become title contenders, it's not possible not any more, and talking of Liverpool losing matches I still think that will also goes with Arsenal as Liverpool might be losing don't you think Arsenal will be losing too, the thing is this season EPL is not really clear on who to win it, because judging from Liverpool signings this season they don't even have to score just one or two goals in any match, and again let's not put all hopes on Liverpool and Arsenal alone Chelsea is also there to compete for the title.