Chelsea could have got the title guaranteed by now ,but they haven't due to poor results during the season like drawing 1-1 to Everton and Newcastle.Also losing 3-0 to Sunderland and you can't lose to these fringe teams while other teams like Manchester United beat them!!
Arsenal on the other hand have also had poor results, but at the end of the season (like losing 2-0 to Bolton) and also quite a few other unexpected results.
Manchester City have been winning crucial games, but have fallen short on other games such as losing 2-1 to Everton. All the same, winning the FA cup has given a boost and they are progessing as the season goes on.
Next season Liverpool will be very good as Carroll and Suarez have flourished at Anfield - they could even win the title!!