I think Liverpool are the most likely culprit, but it will still be difficult for us to usurp one of the top fours current occupants.
Chelsea and Manchester City are the two sides who simply won't become embroiled in a top four fight at any costs given their squad quality and management. The latter might not be the same force as they were last season given their squad restrictions and spending limitations, but they still possess the strongest squad in the league and so many game-changers and players who elevate their performance level above anything their rivals can muster. As for Chelsea, Mourinho sides are notoriously stronger in the second season and he'll undoubtedly refine and mould his team the way which best suits his style. The signing of Costa will improve them sevenfold and is the perfect fit for a Mourinho team. I expect them to win the league and City to compete the whole way.
I expect Arsenal to improve enough to maintain a sizable points margin between themselves and the fifth placed team. They've won their first trophy in years which should have a massive impact on the team mentally, so I'd expect another momentous, run of form at the start of the season. Their weaknesses will likely be addressed and a lot of young players will continue to develop at a fast rate, such as Wilshere possibly, who has stagnated in the last few seasons. I think they'll experience the same short-comings as they do every year with squad depletion however and that might see a similar self-implosion as last season.
Liverpool have been massive beneficiaries of continuity throughout their first squad and having a fresh squad throughout 90% of last season. They will obviously make quite a few additions, but whether they have a sizable contribution is another question. Last season they signed Moses, Mignolet, Sakho, Toure, Aspas and Alberto; One of those was only a real success, with Toure and Sakho impressing at times. Only around 14 or 15 players really played an important role and although Liverpool will be delving into a higher bracket market, it's not a foregone conclusion they will succeed. I expect them to get a bit of a reality check, having to juggle numerous competitions.