With the exception of the new money in Manchester, I think it will be business as usual.
As a Gooner, I am personally confident we will finish in the top 4. Liverpool have improved, but I'm unconvinced by a number of their big money signings, and Spurs have been static for a while. I think the legacy Chelsea squad will make one last push, backed up by a couple of new signings, and run United fairly close.
With regard to bringing in CBs, Wenger should just pay up and have time to blend them into the squad. Defensive chemistry is so important, and we haven't had any for years, and the extra few millions (if that is the stumbling block) in order to bring in players early in the preseason is worth it in this position.
Either way, it's shaping up to be one of the more exciting Premier League seasons, with a lot of clubs posturing.