Arsenal are nothing to worry about. They might get Gyorkeres but they still won't win a trophy that matters.
I do think Chelsea can make a real run for the title. I'm not ready to say they'll win this season because I think Maresca would rather push for a UCL trophy. Chelsea is equipped though now with real squad depth to make a strong run in both Prem/UCL. Joao Pedro and Liam Delap are going to prove to be a huge boost for Palmer. Teams won't be able to zero in on him with 2-3 players marking him anymore. Nicolas Jackson was as passionate as anybody but thank god he won't be playing the 9 anymore.
Sidenote- Nobody is talking about the Enzo/Caicedo price tags anymore and that makes me just as happy.