If the chances for win are accurate (from the Premier League on Google), which are as follows for each of the three:
Liverpool: 63%
Man City: 77%
Arsenal: 83%
Then it's actually more likely than not, that at least one of these three won't win their game (around 60% probability).
Of course, it's hard to put an accurate number on sports events, it's all just estimates mostly based on previous results.
Yes, based on previous results as at the mid season and based on current form.
These predictions are not always accurate, but this one looks like something that can happen because so many football pundits are considering Arsenal to win the League this season probably because of the comeback after they lost to Fulham and West Ham United.
I am in support of Arsenal to win the league as well because they deserve to win since they failed last season due to lack of proper experience and some injuries, but they are well equipped and ready this season, from all indications, Arsenal can go more than ten games unbeaten since almost all their injured players are back.