Eh, I don't see Cahill/Terry/Luiz as good enough defenders for a team looking to compete for the title. Maybe Luiz, who is probably the best of the 3.
I'm probably going to be totally out here, but I'll put my neck on the line and say Di Matteo won't last the season. League form under him was pretty average last year (from what I remember) and it was only the Champs League win which got him the job. With the amount being spent, there's going to be lots of pressure for instant results, with signings that are unproven in the Prem (not going to pretend I know a great deal about any of them, mind)
But what the fuck do I know? Very little is the answer.
EDIT: And you better fucking not get Debuchy haha. We've been trying to tie down a deal for about 2 months now.